As warmer weather comes on, there are more and more posts on A/C matters. Many refer to conversion of a pre-94/95 R-12 system over to use R-134a. I have cautioned against simply buying one of the $30 kits and doing it yourself if you have no A/C experience. Simply put, failure to properly clean and flush out all the R-12 residue and mineral oil can, and in time WILL result in A/C failure. Further, you need to properly evacuate the system prior to recharge. Neither flushing equipment nor a good vacuum pump and gauge set are generally readily available to the home DIY person - and shortcuts here can spell disaster. Can it be done at home? Sure. Here's a good link all about it.

http://www.glue.umd.edu/~singletn/web/pages/acconvert.html

Happy Exploring...

Chris

Great post.

Also, stay away from R134 "alternatives" or you could explode your explorer:eek:

posted elsewhere but to save someone some time I am reposting it here:

Someone asked me in e-mail how I'd do a conversion or recharge. Maybe, for the 2 cents worth and for those who are considering a $30 drop in kit, it might be illustrative to describe a conversion.

First thing is I check the type of refrigerant in the system. Mainly is it "contaminated" ? I have a tester to do this, it tells me the type of refrigerant and the purity. If it is contaminated I stop. In CA disposing of contaminated refrigerant is expensive, so I do not even go further. Many shops are similar. Remember this when you want to put in the whizbang "SUPER R-12 replacement". Often too then contain propane or butane. BANG!

Ok assuming it passes, I next check it for acid. Why ? It often shows a failing system in progress. If it fails it usually means replacement of major components, but I still proceed. I evacuate the system and recover the refrigerant.

Next I disassemble the hoses to/from the compressor, remove the orifice tube and take out the old "receiver/dryer" or "accumulator" (depending on the type of car and what they call it). I now check for signs of black oil. If the acid was high the chances of blackened oil are high. If I find it, I start by assuming I have a system in failure. Often the expansion valve will already be gunked up with the "black crud".

Depending on the severity, I may try and flush the condensor. If I can flush it clean after a couple tries that is a good sign, if not, I assume the system is a total loss and replace the condensor, compressor and receiver/dryer (which gets replaced in 100% of the cases anyway). If I can flush it clean, I then flush everything I can get to. I often start with alcohol and finish with commercial flush.

Rubber hoses get tossed, and replace with barrier hoses. All o-rings get replaced with barrier ones, they are green in color. I replace the receiver dryer and any other inline filter. Any hint of compressor failure previously and I add an inline filter/dryer to the system.

I reassemble everything, add oil along the way (often to the receiver dryer and as a matter of course to a replacement compressor) up to specs.

I replace the schrader valves with new ones. Any rubber sealed part gets treated with NY-LOG - a terrific sealant. I add new connectors at this point too.

I hook up my vacuum pump and pull an initial vacuum. I stop and watch it to make sure it holds vacuum for 15 mins or so with no loss. If it does I restart the pump and run it for an hour. I feel the hoses and parts to see if any moisture has frozen (it will under vacuum). If I feel cold I stop and let it sit a while and then restart the process. I measure the vacuum and look to pull down to 100 to 200 microns or less (a damn good vacuum, near perfect). I have an electronic vacuum gauge that tells me these things.

Finally I connect my manifold set (used to hook up the vacuum pump earlier and monitor the state of vacuum - and at this point hooked into the automobile system high AND low sides) to a can of refrigerant and add liquid refrigerant to the "HIGH SIDE" with the can upside down until the flow stops. Once it has I disconnect it. I hook up a can to the low side port, and place the can in a coffee can of hot water. I can usually now start the engine and there is enough refrigerant for the car to run the AC. The balance of the necessary charge goes in as gas - can upright and into the low side with the car AC operational. NEVER feed a can into the low side upside down. The compressor cannot compress a liquid and a slug of liquid hitting the compressor can damage it. Once I have put in the required amount of freon (from the manufacturer's specs) I'm done.

I check the vent temps, and they are usually around freezing.

So for a usual job, that's it. Compare that to the instructions of your $30 death in a can kit.

Hope that helps.

(p.s. if I am using a 20 lb jug of refrigerant, I will put the jug on a scale and add the factory recommended amount as the charge, easier, but felt it more meaningful to talk about using cans and not jugs.)

Chris

Chris
Very good description and advice on the R12 to R134 conversion.
I had my 1991 Ford Explorer converted in May 2001 by a Ford dealer and looking at my Ford service invoice, I see the parts charges of $49.95 for Retro Kit (FP # 409996)), $29.95 for R134 DY (FP # 528-205), and $28.48 for R134A (YN-19) - for a total of $108.38 for parts - and so I am assuming some of the air conditioning system parts were changed. I wonder where one can find a description of what these parts were or are?
Your vacuum pump which sucks down to pressure of 50 microns (micron = 1/10,000 of a centimeter = micrometer). Hmmmmm, I am not familiar with the micron pressure unit (I have heard of psig, psia, inches Hg, Pascals, etc). I have some 90 lb two stage Edwards vacuum pumps which go down to very low pressure - but as you know, at these low gas pressures the gas flow is in the molecular flow or Knudsen flow regime which implies one needs large diameter hoses or pipes because the gas molecules no longer flow in the normal bulk flow manner.

I cannot say I have any idea what you are talking about at the end of your post. I just know that near the endpoint of pulling a vacuum... you get down into a micron range. My pump (a robinaire) will supposed pull down to 20 microns. My digital gauge starts at 400 microns and goes down to 20. I can usually get 50. There are sites on the web that can conver tthat for you, but it's well into an excellent range for any system. I also know the 134 molecules are MUCH smaller than the r-12 and hence the problems with leakage.

As for Ford parts numbers I can give you no clue. Sorry. I do know that Ford has "kits" for conversion, but know nothing about them.

Chris

Chris
I am talking about the units of pressure measurements - like the air pressure in tire commonly uses the psig or "pounds per square inch gage" unit. To my knowledge, there is no pressure unit of "micron". You are probably reading this off of your instrument (digital implies that the readout on your instrument is digital rather than analog - and digital readouts have been around for at least 25 years on pressure measuring instruments) and the actual units might be "microns of Hg" where Hg stands for mercury. The following web site has conversion factors for many pressure units - and microns of Hg is listed.
http://xtronics.com/reference/convert.htm

The stuff I was talking about at the end of my earlier post has to do with gas flow through pipes. At low pressure (i.e. high vacuum), gases do not flow in an ordinary manner like say water through a pipe (bulk flow). Hence when A/C techicians use those small vacuum pumps to pump down the plumbing on home air conditioning or heat pump systems (before the freon refrigerant is added), it is sort of a joke with regards to actually removing all of the air - and hence many A/C systems have a fair amount of air still in the system (and fortunately the systems will still work with the inert air circulating in the system - but they do not work as well as when most of the inert air is removed). However, if there is some freon refrigerant (R12, R22, R134, etc are all different types of freon) in the piping, and one has a good vacuum pump, it is possible to pump down the plumbing and remove the air along with the freon if the pump is allowed to "pump down" for an extended period of time. If you work in the A/C area and understand high vacuum systems, you are probably very familiar with all this.
Thanks for all your posts.
Mike in Seattle

Mike.. you are undoubtedly correct. Just as we say pull a vacuum of 29 inches, we leave out the unit of measurement. I am sure it is microns of Hg. Vacuum pumps and much newer instrumentation are measured simply in "microns" (check out the Robinaire vacuum pump spec pages for example - most of their pumps are rated at "20 microns").

When you say substantial air remains in a properly evacuated system what level of air molecules are you referring to? It will be well below 1%. It is common practice in some shops to purge a system with nitrogen before evacuating if it is a rebuilt system, to help for just the reasons you mention.

Lastly auto air is not considered a high vacuum application. Other forms of refrigeration (stationary and closed system appliance are considered higher than auto, by far. Once you are in the 400 micron (of Hg.)range you are within the auto air conditioning vacuum arena.
Happy Exploring and thanks for setting the record straight.

Chris

Great thread, I want to jump in.

Vacuum Pump Questions:
1) I've done two A/C conversions using the Robinair venturi pump that pulls down to 29mmHG. They both seemed to do well last summer, but I no longer have the vehicles. I may need to do the process on my Mountaineer, so I want to know your opinion on these venturi pumps.

In the for what it's worth category... Last summer I did a Honda repair ... replaced the compressor and receiver dryer. It was an R-12 system and stayed R-12 (eg. no conversion). I was out of town and it was a favor for a friend. I had forgotten my electric vacuum pump, but he had a Harbor Freight venturi type. I used it, and ran it for about half an hour (his air compressor was starting to overheat. The vacuum looked ok on the gauge set. I refilled it with R-12 and it seemed to work fine, although the vent temps were a tad higher than I was expecting. The charge was correct as per factory specs btw.

Recently he visited and I asked to check to see how the charge was - if there was any residual air. My equip said 2%! I never get an air reading using electric vacuum pumps to evacuate, and then I usually run them for 45 mins minimum, often longer (although the vacuum pumps get real hot too!).

My take on the little venturi types? Ok, better than nothing, but a long ways from an electric one.
My electrics are 1/2 and 3/4 horsepower.

Lastly, those venturi types can use more air than many homeowner air compressors can reliably deliver constantly.

HTH..... Chris

Chris, Thanks for the heads up!

I have a question about charging by pressures instead of by weight:

What are the ideal pressures for high/low in your opinion when the system is running optimally? I use the rule of thumb that high side should be 2.2 * ambient degrees F. Sound good? What do you think about low side?

Also, one about flushing:

I used brake cleaner and compressed air to flush the systems when I did the Peugeots, but I've heard other people say use Isoproyl Alcohol, others use a dedicated AC flush chemical. What's your prefference?

V8... To start with, there is no "perfect high side or low side pressure". The idea is to make sure you have enough refrigerant to expand thoughout the evaporator - that will acheive maximunm efficiency. If I am adding by pressure, I'll generally look for a sightglass, and if I cannot find one I have an electronic sightglass I can use if I get really perplexed, but usually a starting high side of 2.2 ambient is a goodplace to start. I watch low side drawdown with the compressor running and measure and monitor vent temps... You will often see them fall, and once you have too much they will rise. Fine tuning can be frustrating. One of the nice things about totally evacuating is that you have a much better idea since you can find factory amounts for charge and oil. When just adding to a system there is always that nagging Q about oil... on a recharge there isn't.

Returning briefly to the subject of Microns MikeP brought up, I found a pretty good link on the subject.

http://www.aircondition.com/wwwboard/2002Q1/70213.html

Also I have a chart that says at zero vacuum there is a measurement of 760,000 microns. 500 microns equals 29.902 inches of mercury, 100 microns equals 29.917 inches of mercury and 50 microns equals 29.919 inches of mercury, with an absolute pressure PSIA of .001.

Hope this clarifies things.

Chris

V8 - As I read my reply I didn't want you to think I was trying to dodge your question. a low side pressure should be in the approximate range of 25-45, but will vary as the clutch cycles. It's all about fine tuning.

Chris-

Thanks for the replies - you really know your AC!! I've also learned a lot from the forum you posted above, http://www.aircondition.com/wwwboard/index.htm - I suggest that everyone interested in AC systems check it out.

V-8... I also see I did not reply to your post regarding flushing. Brake cleaner is ok, so long as it is not the chlorinated type. Most of the ones that are not will say so on the can. I like alcohol along the way because it bonds with water and helps remove residual moisture - an AC's enemy. I nearly always follow up at the end with an Ester based flush. If I stay R-12 ester oil and mineral oil are compatible. If I am changing to R-134 I always use ester oil in the changeover.

Yes the airconditioning.com site is a great one, and there are other similar good sites. Be warned you will see differing opinions, this stuff is not always an exact science.

For what it is worth, I recommend against any refrigerant that is neither pure R-12 or pure R-134. The mixes create a host of problems if you ever take your car into a shop to work on the AC after you've fiddled with alternate refrigerants. There are really smart folks who will disagree with me. For me, I stay with the straight stuff. And like I said before, if I encounter a system with a blend in it, I WILL NOT WORK ON IT. I am not alone.

V-8, and others, if you have not invested the 75 bucks or so (or less) a good gauge set costs, do it, E-bay has em all the time. They are worth their weight in gold if you are working on AC. The gizmos and gadgets I have are nice, but the gauge set is primary. As you will notice on some websites where they dispense free advice from really good folks, they always want to know 4 things... ambient air, hi side pressure, lo side pressure and vent temp. You need a gauge set for 2 of those. Oh and as a postscript... I bought several digital readout thermometers from Harbor frieght... I live and die by those guys. ANd they are under $10! Great in the vents.

Happy Exploring


Chris

Happy Exploring

Gauges were the very first thing I ever bought, got a decent deal at Autozone. I wouldn't even think of doing anything without them! It's pretty much impossible to do any kind of AC work without them. I also have a thermometer probe for my Mac Multimeter - an invaluable tool.

I must be one of the lucky ones! Three years ago i took my 93 Ranger to the shop for AC recharge. I was informed there was a bad leak in the condenser. The repair cost was going to be close to $600.00. I went to Wally World and picked up a conversion kit and a can of R134 stop leak. That was three years ago, last week i added one half of one can of R134 to the system. The air coming out is very cold! Ben

Ben..

Don't misunderstand, I think that's great and hope it stays that way. Let me try and clarify a couple things. First let's examine the diagnosis and proposed charges. You did in all probability have a condensor leak, how bad is questionable. That meant you had zero refrigerant charge (a good thing as we will see in a minute). $600? well, a leaky condensor could be sent out for repair, slight savings, and if it leaked in one spot, another is likely soon behind. Not a good bet for a shop, and at the cost of R-12, not something you'd want a come back on. Cost of a new condensor ? $150 to $225 depending. Oh since the system was open, a new receiver dryer. Cost? $75 or so. Since you don't know what happened to your oil charge, a flush and total recharge would be wise. Cost of material ? $100 - $150. The rest would be labor. $600 was in the ballpark in other words. They were not trying to rip you off.

Now, I have some doubts about the size of your leak. Stop leak has a place, but think about it, if it could plug a BIG hole, why wouldn't it plug up the expansion valve, that hole in it ain't all THAT big. It apparently worked for you, and like I said that's great.

Some of the problems I see with the $30 kits are: if there is residual R-12 people add the kit in right on top of it, mixing refrigerants... a no no. If there is a charge, some simply vent it to the amosphere (a federal crime these a days and not good for the environment. - I'll bet the kit tells you to take your car to a shop have have them recover any remaining R-12 before adding the kit. YEAH right!) Next the oil. Auto air conditioners are like 2 cycle engines in that their lubrication is carried in another medium. Here in the refrigerant. R-12 systems use mineral oil. Mineral oil, is not, for all practical purposes soluable in R-134. So it won't carry it through the system for lubrication. PAG or Ester oil is soluable in 134, so that's what gets used. PAG and ester (POE) are not at all compatible. PAG and mineral are not either. POE and mineral coexist. Some think when you have ESTER added to a mineral oil system with 134 any excess mineral oil migrates to low points and sits. Me, I dunno, I spoze so. But how can you know the state of an oil charge when adding ester oil in a changeover kit? I wonder how they calculate these things into a one size fits all arrangement.

So you probably had the best possible scenario for a changeover kit, and met all the "one size fits all" designer's assumptions. I'm glad it worked and that you are happy. I see far too many that are not.

Happy Exploring

Chris

Ok.. one last comment here... based on a conversation I had with some buddies today. We were talking about this thread and about Ben's post in particular. Someone said to me "You aren't going to stop those who want to invest $30 bucks in a kit from doing so. They don't have working air to start with, if it works for a while great, if it trashes their system, they are not any worse off." And then ," You'd do better by telling them when and how to use those kits."

I gave it a lot of thought today, and I suppose there is some truth in what he said. So, with the initial warning that I do not endorse nor recommend these $30-$40 reftorfit kits, and in the vast majority of cases think you do more harm than good.... let me try and see if I can come up with some recommendations.

First. When is a kit NOT appropriate. Hmm, if you have a crumped compressor, do not replace just the compressor and add a kit. Usually a bad compressor will have contaminated a system beyond your imagination in its death throes. The only sure fix is to flush and replace whatever cannot be successfully flushed. Oh and if you EVER have a system open, always replace the receiver/dryer (or accumulator depending of the manufacturer and type of car - same thing more or less for our purposes). Another - you have a 93 and earlier system (or some 94's were also R-12). The cooling is there but low. DO NOT JUST ADD A KIT. (see below). I am sure there are other times a kit may not be appropriate, but that all I can think of at this instant. (bearing in mind I do not think a kit is EVER a really good idea)

NEXT... When might we try a kit. Ok... You have an otherwise semingly good system that gradually over time seems to blow warmer and warmer air until it stopped blowing cool air altogether. We can assume there is a slow leak and you lost your charge of R-12, or most of it.

Here's the rub here. R-134 molecules are significantly smaller than R-12. If you had an R-12 leak, imagine the leak rate with R-134. Can you fix leaks? sometimes. And sometimes the leak fixer stuff in cans might work (see Ben's post). Two most common leak areas ? Compressor seal (fixable but not for 99% of DIY'ers) or valve cores. The valve cores in an R-12 stem look like big bicycle tire schraders - and in fact they more or less are. Screw right in and out in the same fashion. A definite DIY job to replace these ASSUMING THERE IS NO REFRIGERANT CHARGE. Bad news about refrigerant (some call it freon, but that is a DuPont trade name so I try and call it refrigerant) if some squirts you in the eye, you WILL lose the cornea or sight in that eye. Goggles or suitable eye protection are a must while working on a system with any charge in it. "Well" you ask "How do I know if I have a charge? Can I hook up a simple gauge from the $40 kit and see ? Yes and no. The AC will not operate if the charge falls to a certain level. If the AC is not operating, and there is enough freon to saturate the system (not a lot needed for this) the pressure will be the same in a non operating low charged system as it would be with a full charge. Put another way if you put 6 oz of refrigerant in a closed 5 gallon container it would read the saturated pressure of the refrigerant(pretty close in PSI to degrees farenheit at normal temps, eg. 70 PSI at 70 degrees). If you filled it 3/4's full, it would read the same. So reading a partially charged system in a static or non operating state won't help you determine anything. If the charge is so low you cannot run the system, you KNOW you are really low, just not HOW low. NOW folks, understand venting R-12 into the atmosphere is against the law. The fine is extremely high. But I have seen some folks will try a little test, figuring a little vented to fix a system is better than refilling one and letting the entire charge bleed away. What these folks do is to use a little stick or small screwdriver and press down on the schrader valve for about 5 seconds and see if the hissing stays the same or starts to lessen- these same folks ALWAYS have eye protection when I have seen this. IF i the hissing stays the same there is probably a decent amount of refrigerant in the system. If is falls off, they stay with it and bled off what in all probability was a VERY slight remaining charge, until it is gone.
If the charge is a decent one (good steady hiss), it should be recovered by someone with the equipment o do this. I'll offer no other ideas or suggestions, PERIOD. Mind you I am not suggesting the former either, just telling you what I have seen in my long life.

So with your charge gone, either my leaking away to by being recovered, next what? Ok here is where I differ greatly with the kit idea. You spent $30-$40 on a kit. Have access to an air compressor? Buy one of those $15 Harbor Freight venturi air pumps. Buy a single r-12 hose with a shut off on one end. (another $15). Connect this to the valve on the high pressure side. .This is the smaller line running from the compressor to the condensor in front of the radiator - or maybe just after the condensor running back to the receiver/dryer again, it varies, the line will be the smaller, usually metal, ) Hook the other end to this venturi pump and hook up an air compressor. Run this as long as your compressor can stand it... 30 mins should be good. (relatively speaking). Add the changeover fitting to the other valve (the one on the bigger hose leading from the firewall of the car to the compressor or maybe on the receiver dryer AFTER the expansion valve - it varies. If it is on a line, the line will be the bigger of the two. ) do this while the vacuum pump is running). When you have run the pump as long as you can or at least 30 mins if able close the valve on the hose and shut off the pump (shut off the air compressor in other words) connect the 1st can up from the kit and let it run into the low side UPSIDE DOWN. (I know I said NEVER, but the kit ONLY has a low pressure fitting, and if the system is not running this is safe. NEVER DO THIS ON AN OPERATING SYSTEM, EVER EVER EVER!!) It should take the entire can. Let it sit a few minutes to equalize in the system - eg. vaporize past the expansion valve until the pressure is equal on both the high and low sides of the system. Quickly unscrew the hose from the high side fitting. There should be adequate system pressure there now to keep air from leaking in, in fact some refrigerant may leak out as you unscrew it, that's ok.

Next, start the car and see if the AC will operate on this level of charge. If it does, the rest of the rerigerant goes in on the low pressure side, can RIGHT SIDE UP. A can or pan of hot water to float the can in as the refrigerants is fed into the system helps speed the process. More or less follow the kit directions at this point.

That's the best advice I can give. I don't believe in the kits. I do not recommend them, but if you absolutely have to use one, maybe this will help.

Happy Exploring

Chris

Chris' advice is top notch, but I feel slightly different on the kits. I think with the addition of a venturi vacuum pump and a real manifold gauge set, A/C conversions can be done sucessfully for about $100 + evac. The manufacturers really should sell kits complete with a manifold and pump, or at least tell people.

The low-pressure only gauges that you can buy are worthless. Also, not having a manifold makes the A/C work extremely difficult. If you want to do the conversion, use a kit. It will be a great chance to learn about another system in the truck and most likely save some money. Thank god A/C can be done by the DIYer, and I give props to companies like Interdynamics for giving us that ability.

Evening V8.... I think with your post we may have finally come full circle here. I think I started with the idea that AC COULD be DIY, and linked to a post on it. I was just unfavorable on the "kit" approach. If someone wants to do their OWN AC they can... like you however they really kind of need a gauge set to start out properly. In some localities rental places will rent a vacuum pump. For a cash outlay of under $125 you can have most of what you need, (save the pump for evac) to flush, evacuate and repair your own. As you accurately point out the little low pressure vacuum gauge with the kits is all but worthless. My point was that you may need to do more than the simple kit explains to you, not that it could only be done by a pro.

We all come to this site to learn how to do our own work. Some are adventurous and capable, others just want to see what they MIGHT be able to handle. Between us we've covered that ground...So see, we don't disagree all that much, and we've both added to the collective knowledge here. Thanks !


Happy Exploring...

Chris

Hello again, i didn't mean to step on any toes here. When i posted about my own inexpensive conversion from R-12 i was only relating my own personal experience with the kit. It was three years ago when i noticed my air conditioner had quit working on my 93 Ranger. I took it to the shop and explained that it had slowly lost it's cooling ability over a period of time which it had. They assumed,just as i had that it was just low on R-12 no big deal. They pumped 2 pounds more or less into the system and wholla, i had functional air once again. Cost for this was around $90.00. I made it just about six miles down the road when the air turned warm once again. Took it back and they did a leak test,found the leak and quoted me the $600.00 fix it charge. At that time it was either fix it my self or no air! It still works great after three years(knock on wood big time) I guess i must be the luckiest (s.o.b) on the planet to have regained the use of my air conditioner for less than 10% of what a professional would have charged for fixing it. Last but,not least i've read an article or two on what a contrived bunch of crap the effects of R-12 were to the enviroment. Ben

I just remembered something that had slipped my mind. My Nephew was an ace chevy mechanic at a large dealership. We discussed this subject in detail years ago when the conversion to R134a was just starting. In their shop they were doing a lot of conversions and they were going the whole route. They evaced the system, changed all the O-rings,pulled the compressor and tipped it upside down to get the last drop of residual oil from the R-12 out of the system. He told me the amount they got out after the evac would barely cover the end of his thumb. They concluded it wasn't worth the effort. After the inital evac they just pumped in the r134a oil and refilled with r134a period. Ben

Chris
Outstanding writeups! Many thanks!!!
It should be noted that the Freon R12 is banned from manufacture in the United States - but the Montreal Protocol allows many countries to continue production until 2010. See the link:
http://www.china.org.cn/english/environment/62914.htm
It is my understanding that the chemical companies who manufacture Freons did and do not object to the bans on R12 because they are able to sell the other approved Freons for higher prices - hence their profits on the sales of refrigerants have increased. And the effect of the atmospheric ozone depletion on increased uv radiation at the earth's surface is true for areas like Antartica, Australia, New Zealand, southern Chile, etc. but probably not true for the United States and most of the rest of the world (ground level). And upper air measurements have shown that the depletion of the ozone layer is decreasing so it is a success story. The EPA internet web site providing information to the public on uv radiation (updated daily) is based on CALCULATED uv radiation at the earth's surface for many specific regions of the US - because the MEASURED uv radiation at the earth's surface in the US has been steadily decreasing with the years (possibly because of increased lower level air pollution including ozone). My apologies for the off-topic discussion - but it is related to all the hasstle of converting from R12 to other refrigerants in our Ford Explorers. This phasing out of R12 is a money maker for the Freon manufacturers and the air conditioning supply and repair folks - but a pain in the ____ for many of us users.
Have a good day.
Mike in a dry but cool Seattle.

Chris, and others:

My 1997 (109k miles) Mountaineer's R134a AC system *may* not be working.

Ambient Temp: 58.0 degrees F
Static System Pressure: 55psi

When I turn the dash control to "Max AC" and put the fan on high, temp all the way cool, the compressor will turn on for about 2 seconds, then shut off. The Low side pressure will dip to about 25psi, and the High side will go to around 70psi. When the compressor shuts off, both sides return to their 55psi static value. About 15 seconds later, the compressor will turn on again, and the process will repeat.

The 134a that was left in my manifold hoses was dyed bright green, similar to the color of antifreeze. Did Ford add the dye at the factory, or has a shop worked on it?

I suspect the high-side valve core is the culprit of the refrigerant discharge. When disconnecting it, there was a much larger "spurt" than when disconnecting the low side. However, I would like to not have to open the system and replace components if necessary.

My thoughts right now are to:
1) Wait for a warmer day to check the system in case it is a thermostat issue. Unlikely, since the AC system's pressure behavior.
2) Just add more 134a untill the high side pressure is somewhere in the ballpark of 2.2*ambient.

What are your thoughs? Opinions?

NOTE: I have moved this problem to a new thread:
http://www.explorerforum.com/forums/showthread.php?s=&threadid=78901

V8.. Your static pressure won't help us much since it would be the same almost without regard to the charge state (unless you were nearly totally out of refrigerant). Your compressor cuts out because of the low pressure switch, it's operating properly. I'd say it's pretty clear you are low on R-134. I'd add some. Also don't get all hung up on 2.2 x ambient and all that, especially at low temperatures. Add freon, watch your pressures and monitor your vents. And on colder days, you will have it cutting out a couple times a minute or more (I have to find that chart on cut out times) even when everything is just perfect.


Happy Exploring

Chris

Mike... thanks for the compliment. Good link on the R-12 ozone issues. One note though, the AC industry isn't really making a killing because of this. The labor prices are the same regardless of the system, 134 or R12. A jug of 134 costs about $100 (as of last summer) and a jug of R-12 costs me $750.


Happy Exploring

Chris

Ben... thanks for the followup. I find with my recovery equipment, if I evacuate an operating system I will usually get an amount of oil in my oil separator equal to 50-70% of system capacity (esp if I have operated it up to the point of beginning my evacuation and recovery). As for the rest, some will reside in the receiver dryer, some in the compressor, some maybe in the condensor and a bunch lining all the piping and hoses, etc I suppose. I think I mentioned in one of my posts the thinking that the old oil migrates to low points and stays put when you go to Ester in a changeover. I have no idea, but you CAN get quite a lot of oil out with the right equipment. Some of the older equipment did not separate the oil from the refrigerant, and in those cases, they were pulling it out like I am, they just didn't know it.

Happy exploring

Chris

Just so were all on the same page. I still see R-12 for sale once in a while here in Minnesota. It's usually in the classified section of the paper. I've been told this stuff is still being blackmarketed out of Mexico. Ben

Ben:

You are partially correct. The actual manufacture-ban of R-12 by the signatory countries started in 1996 as I recall. However they apparently went full tilt up til then, because there is still quality (eg. DuPont, Sercon etc) virgin (e.g. not reclaimed) R-12 out there. As it gets used up the prices go up, hence the black market stuff. Most shops now check every new tank with equipment to measure purity and contamination. So for now, R-12 is around, just VERY pricey. Oh and, you need a license to buy it.

I wanted to mention another thing. The refrigerant R-134 you buy at AutoZone Pep Boys etc is the exact same stuff the pros use, chemical composition wise. Pure 134 is pure 134. Someone somwhere else on here suggested it was bad stuff and harmful to your system. THAT is hooey. I suspect someone heard an AC tech mention that there is some evidence that the "O-ring conditioners" and "leak sealers" may..MAY.. over time be detrimental, and those places do sell combined cans of 134 with those additives also. But the pure 134 is fine.

Happy Exploring

Chris

When i say that R-12 is still being sold here in Minnesota,in the classified section of the newspaper. I'm referring to the private, used auto parts section of the paper open to all. As in no license required. Yes,i'm aware you need a license to buy R-12. You also are supposed to have a license to carry a handgun here,but there are plenty that don't follow that law either. Ben

On the subject of flushing... something I think is important in any conversion for everything but the compressor and evaporator... the tools for this are simple, but never discussed. I have an old flusher that uses air and like it. There are DIY knock-offs that are perfect for the DIY'er for $35 (or less). More DIY'er's should flush, so here's apost I posted elsewhere with the info on cheap flushers (air powered):

Out of curiosity I checked a good supplier with an e xcellent online link to see what their flushers are going for these days. The link is www.mvpro.com. Their flushers are only $35 and they have a special on ones with dented flush cylinders for $22. WELL within the DIY budget!!

Happy exploring

Chris

Chris
Many thanks for the internet link which has the "Handy Dandy Flash Guns" for $34.99. Is there a writeup on the procedure and equipment flow system for doing a R134 AC system flush using this a flusher like the "Handy Dandy Flash Gun" somewhere on the internet or in your prior posts? Thanks for the continuing information on this topic.
Mike with 91 4x4 in Seattle

Mike...

The usual procedure is to unhook all the connections to give you access... since the system is open and you are going to replace the receiver drier/accumulator anyway (more on that below) you are already part way into it. The general idea is to blow flush through anything you can EXCEPT... the compressor (which is not a clear shot through and which could possibly be damaged) and the evaporator. Mainly this means the lines and the condensor, which is where most of the crap ends up it seems. The receiver/dryer will be new, and hence clean as a whistle <g>.

Why replace the receiver dryer some ask? Well the dessicant in this puppy holds maybe 20-30 droplets of moisture before it is saturated, and the filter material has probably done it's best work in 50,000 miles. Since you are introducing moisture into the system if it is opened, and since you are there anyway... the standard mantra is REPLACE. Not from the junkyard, btw. But new.

I have various sizes of clear plastic tubing I hook to the output end of the part being flushed... I find it easier to collect the flush that way.. I want to SEE it, and some components do not end in convenient places to recover the flush. The flush should come out clean. I REALLY really tried recently on a Ford Explorer condensor which had black death to get it clean... used everything I could think of, including MEK, just to see.. nope. When they are like that, replace em. <sigh>.

Why not evaporators? Well they are in many ways protected by the expansion valve. Not a lot can get in there. They also have in many cases a screen inlet. General practice is to let em be, but some try and do em. I don't. BUT in a black death system rebuild it's always a good idea to put a filter downstream of that item if you can. (inline add on). R-134 systems and barrier hoses present special challenges to add on filters though.

As to technique, some like to use a "Pop off "procedure, where they use their finger to plug the end of the line or component they flush and let it go in episodic intervals, "popping off" the pressure. Me, I let it run and do it over. Try both and see, you may find the other idea merit worthy. in A/C there as many ideas and many heart felt notions as anywhere. No one has the intellectual high ground. Smart people will disagree on many points.

Hope all this made sense and helps.


Happy Exploring


Chris

I should have added to the previous post on flushing evaporators, if you do it, REVERSE flush them. Opposite the direction of flow. It's the screen thing.

Happy Exploring

Chris

The subject of blended refrigerants (Hotshot, Duracool, Freezone etc) came up in another A/C thread and thought maybe this might be a good place to post this. I'd add on the issue of Duracool, many states make the use of hydrocarbon (eg falmmable) refrigerants illegal. I would also add that Frigidaire is touting it's own blend, but not for mobile A/C. Blends seem to have found a better use in home A/c and stationary refrigeration than in mobile A/C.

Blends. Let's talk about them.

There are some blends that, in my belief, in time will become accepted. A Ton (most) of em are rotten. Hey they are refrigerants and they work so what's the big deal? Well a couple of issues. First. Fractionalization.

Fractionalization - What's that?

It's the tendency for a blend to try and revert to it's component parts. The more volatile can leak away leaving the less desirable.

Next is oil miscability. Miscability is the ability of oil to dissolve in and be carried by the oil. This is how your compressor gets it's lubrication, remember? Not all refrigerant carries oil well. Some of the blends have a volatile component designed to be the carrier... hmmm if THAT leaks away... go figure THAT one out - no oil, no compressor. Others simply do a poorer job of carrying oil than 134a. And WHICH oil is always a question. Varying blends do better with differing oils.

Finally... if you use a blend, most shops do not want to fool with the system. Because they didn't do the work and want to punish you? No, because by law THEY have to reclaim the refrigerant, and a blend is VERY expensive to dispose of, they cannot reuse it. Simple as that.

Watch out for exxagerated claims on blends. If it sounds too true to be good, it is. If blends were so great why did R-12 remain the choice for so long?

food for thought...

Happy exploring.

Chris

OK we've opened Pandora's box on blended refrigerants, maybe more info may prove helpful to some, irritating to others, anyway....

By the time I find all my old information and post it, everyone is gonna be sick of this thread, but under the notion that too much information may be better than not enough, here's some interesting info on blends:

FRIGC or FR-12 = 39% HCFC-124+59%HRC-134a+2%butane (flammable in quantity)

Free Zone aka
RB-276 = 19% HCFC-142b+79% HFC-134a+2% syn lubricant

McCool, aka
R-406A = 55% R-22+ 41% HCFC-142b+4% isobutane
(flammable in quantity)

Autofrost, aka
Chillit, aka
GHG-X4 51% HCFC-22+28.5%HCFC-124+16.5% HCFC-142b+4% isobutane (flammable in quantity)

Hot Shot, aka
R-414b, aka
Kar Kool = 50% HCFC-22+39%HCFC-124+9.5%GCFC-142b+1.5% isobutane (flammable in quantity)

Freeze-12 20% HCFC-142b+80%HFC 134a (hmmm)

Forget the HCFC and HFC, substitute R, and HFC 134a becomes R-134a etc, which is more usual in nomenclature. The EPA has approved these blends subject to proper fittings, hoses etc.

None of these are suggested as simple "drop-in" substitutes. (eg. pump em into an R-12 system as is) I found it funny that Freeze-12 was basically R-134a anyway.

Like I said earlier time may tell the tale on blends. The issues are out there. I'd either pay to stay with R-12 or switch to R-134a before I went exploring blends. Tempting I know... but.....

Hope this helps someone...

Happy (and cool) exploring

Chris

ps. If ya JUST Gotta do a blend, my money is on RB-276
(even labeled as a Blend by the B!- or sold as Freezone - but that said, I do NOT recommend it or any blended refrigerant for the DIY'er!)

When my dad bought my Explorer in '97 the Ford Dealer had done the retrofit to R134 for which I am glad because R134 is so much easier to obtain than R12 for which my dad and I had to search high and low to find for our 4640 John Deere farm tractor. What was odd tho was that the Explorer still had its stock fittings, however, they wouldn't fit my dad's R12 equipment nor his R134a eqiupment which was a "gift" from his previous employer. There are those little quick coupler nipples you can buy from Auto Zone and screw onto your older fittings when converting. It's handier than threaded couplings.

VBBoatBuilder just posted a really excellent message, with accompanying photos on the subject of his repair/recharge. I HIGHLY recommend you all go look at it!

http://www.explorerforum.com/forums/showthread.php?s=&threadid=78901


Happy exploring

Chris

http://www.imcool.com/articles/aircondition/corroded_accumulator.htm

The A/C clutch is controlled by the A/C cycling switch (19E561) and the A/C pressure cut-off switch, which are connected in series. The A/C cycling switch is mounted on the suction accumulator/drier (19C836), and the A/C pressure cut-off switch is mounted in the discharge line at the A/C condenser.

The A/C cycling switch closes when the pressure on the low side of the system reaches approximately 276-324 kPa (40-47 psi). The A/C cycling switch opens when the pressure drops to approximately 163-175 kPa (23.5-25.5 psi), disengaging the A/C clutch. In ambient temperatures below -1º C (30º F), the A/C cycling switch will not allow compressor operation because of low system pressures.

The A/C pressure cut-off switch is used to interrupt A/C clutch operation in the event of high system discharge pressures. The A/C pressure cut-off switch is a single-function switch that controls A/C clutch engagement. When compressor head pressures rise to approximately 2896 kPa (420 psi), the contacts open, disengaging the A/C clutch. When the pressures drop to approximately 1724 kPa (250 psi), the contacts close to allow A/C clutch operation.

I converted my A/C with the $30 kit 2 years ago. Took 15 minutes with no tools. Changing the air filter is more involved.

Well, I had a similar experience...My cousin is a mechanic licensed in a/c repair...I took my Ranger to him last year for conversion..Fellows, lemme tell you, it's not exactly cheap!! There was zero charge in the system, so he disassembled the system, flushed lines, replaced reciever/dryer, orfice and used ester oil for the recharge.
It has been a very worthwhile investment as a year later it will still make you shiver!! I'm getting ready to haul my 92 Explorer Sport in for the conversion as well...I'll be thanking myself soon enough as July nears!!:cool:

Sax that was a good job then I'm sure. It will last you a good while. Congrats for having it done that way and springing for the bucks now, rather than a system replacement in a few years.

happy exploring


Chris

No offense meant to anyone.

hello to all
just thought i would let you know that i converted my system over like 3 years ago, myself // i use to do ac work at a local rad shop // so i had all the tools // there was a stink before about having to change the dryer, oil, orfice tube compresser ect........... not likley, i evacuated the system, pulled the line off of the dryer, added 3 oz of the new 134A oil to the system, along with the old R12 stuff, put it together again, changed the fittings, vacummed the system, then when i got a good reading from the vaccume, i put the 134A freon in, but the secret is to read off eather the evaprater box, sometimes on the dryer, the old R12 amout of freon needed, and drop a 1/4 lb of freon.

try it you will be impressed, revving my truck at normal driveing rpm's (1500), the system will blow out 6 degrees, and i have not touched it since this year when i checked that i lost no freon over the winter.

I ran into a situation recently that made me think I should have mentioned something important but didn't. Valve CAPS !

Believe it or not... the valves are a common leak point, especially in 134 systems since the molecules are smaller and leak out more readily. Often we see caps as just "dust covers" but they are actually part of the system sealing defense. If yours are absent, get new ones and put them on. Lube the inner rubber seal with mineral oil if you have it. I can't tell you how often I remove a cap and hear a slight hiss.... it was doing it's job. Just an afterthought.

Cool Exploring


Chris

ps. equally true on older pre 95-96 R-12 systems !

Just a quick note about units of measurement and vacuum:

mm means millimeters, microns are typically represented my a lowercase "u"

When expressing vacuum or pressure in "x" mm HG, what that means is "This vacuum is strong enough to pick up a column of mercury that's "x" tall?

If you'd like a peek at a handy dandy conversion chart in order to get to psi, gm/cm^2, etc etc, etc, the nice precision measuring equipment folks have just the web page for you!

http://www.pmel.org/HandBook/HBpage25.htm

Regards,

A_G, former Florida Army National Guard 35H (Calibration Specialist)

Alpha... thanks, good post. did a photo post of a recharge on a rebuilt system, thought it ought to have a link here, so here it is:


http://www.explorerforum.com/forums/showthread.php?threadid=84675&referrerid=15286

Happy and Cool Exploring to all

Chris

yeh...i tried the conversion kit, lost 20 oz of r134 OVERNIGHT...and all that money and ozone destroying stuff was out completely...so i figured i had a leak, put in some with the dye in it and used a black light, couldnt find a leak and that coolant lasted for a couple more days (almost as if the stopleak did its job) and now I either dont have enough pressure in the system to make the compressor kick in, or it leaked out...though I have a small amount of pressure in the high pressure side......but the moral of the story is (in my opinion) those conversion kits are junk, and AC is enough of a specialized system (like a tranny) that if you dont have the time and energy and means to retrofit and AC system THE RIGHT WAY its not worth the time and im going to take it to guys that do it all the time cause I gave up

It's that time of year again (bump)

Ha! Thanks to my dad, there's a surplus of about a dozen R12 cans out in the barn that he picked up form Car Quest like right when it was made illegal. I'm sure it'll come in handy someday. (Las, I think I have factory R134a, I'll check again)

My '93 Navajo is needing the R134a upgrade. I looked at the pressure switch and there is no adj. Do I need to change out the switche(s). Thanks and great posts everybody. This is what these forums should be but seldom are.

Adale... you can convert without any changes. The only recommended change is generally to add a high pressure cutout for 134a. If I recall this cuts out when head pressures reach 440 pounds. I think FORD has a retrofit, and Classic Tool Design has their own add on as well. I've done conversions where I have not changed a thing....and candidly, an adjustable low cutout is a recipe for people to fool around and end up with frozen evaporators. The non-adjustable is fine. On another note, there is a variable orifice expansion valve on the market. I had stayed away but may be a guinea pig to see if it works as advertised. It might be a fun "exploration". I'd definitely check or change the expansion valve on the changeover.

You're a prince Glacier. So you are saying to change the expansion valve? To what? Is there a specific one for R134a?

The expansion valve (actually it is an ofifice tube, and I tend to call it an expansion valve - same function - see note in the following post) for the old R-12 will work fine with R-134a, but you pose a good question I have not researched - IS there enough difference to warrant a different expansion valve? I'll check and post what I find. My caution was just to make sure it was clean and free of any debris.

Glacier, are you referring to the orfice tube as the expansion valve? Also where do you mount the high pressure cut off switch ?

Yes I am using those terms interchangeably. As for the hi pressure cutout, the version you get will instruct you where to mount it.

Finally completed this! Wasn't real hard just time consuming and getting to some of the fitting, like were the orfice tube is, was a real PITA! A couple words of caution, be careful when putting the R12 to R134a adapters on the manifold hose, it will break easily, don't ask, and yes it was expensive. Also be sure to pull a vacuum at least one hour, possibly more if it is a humid day. Also there have been a lot of posts about the vacuum measurements when doing this. Remember you really are evacuating the system not simply vacuuming it out, that is why you measure the vacuum in microns and not inHg. BTW on a 75 deg day, with 80%+ humidity, my system now puts out 39 to 40 degree at idle and makes a really big puddle of water quickly. I drove it to work today, and it is supposed to be 70 deg, so we will see what happens!
Thanks to all and a special thanks to Glacier your posts and insight saved me big $$$ and I am sure a bigger head ache.

Glad to hear you pulled it off. Happy I was able to help. This is how I see this forum excelling... sharing what we collectively know.

ok do u have to chnage the oil if u swtich to 134a i have heard dif things

ok do u have to chnage the oil if u swtich to 134a i have heard dif things

I think that's covered in this long thread, but your short answer is yes. Flush the system and use ester oil would be my recommendation.

Great info!

But my question is, in my '93, my A/C (R12) works fine. Should I convert to R134a just to do it?

At some point in the future, I will replace the engine. Since I will need to open up the A/C, should I change then? BTW, I have 3 cans (12 oz.) of R12 that I bought many years ago ($2 a can!).

Great info!

But my question is, in my '93, my A/C (R12) works fine. Should I convert to R134a just to do it?

At some point in the future, I will replace the engine. Since I will need to open up the A/C, should I change then? BTW, I have 3 cans (12 oz.) of R12 that I bought many years ago ($2 a can!).

Don't open an A/C system unless you have too, why spend the $$$. A proper conversion isn't cheap. However, when you pull the engine, you will need to discharge your A/C system. If it's open to the air for a while, you'll also need to change the accumulator as it contains a dissicant that will quickly be ruined by ambient moisture.

Since you have R12, it's a 50/50 whether to stay R12 or convert to R134. If it was me, I'd convert. By evacuating the system and replacing the accumulator - you've put in most of the hard parts necessary for a proper conversion. It will save time and $$ down the road, if you need to work on the A/C system again.

On this point I respectfully disagree with my good friend V8Boatbuilder. IF you do not have a need to, don't convert. IF you have enough r-12 to STAY r-12 after repairs (and you do) STAY r-12. Those systems were designed around r-12 and work best using it. 134 conversions tax the condensor's capacity to get rid of the heat - 134 designs have a bigger condensor. Me? I have a 92. It is r-12. I totally rebuillt it a few years ago and it's r-12. Hasn't lost any refrigerant so far... if I replace the system ever again? r-12 for me.

It helps to have r-12 available to you. You have some. So my advice is... stay r-12.
(regards to Aaron - there's no right or wrong answer here... just opinions.)

Thanks for the opinions - I think I will stay R12. I understand the reasons for converting, but I do have some "extra" R12.

Is the factory condensor sized OK to function properly with R134a? I had heard that a true 134a condensor needed to be larger. This has to do with the properties of 134a (vs. 12). If so, I would assume the evaporator should be larger too, right?

HI there!
My '92 Eddie Bauer compressor just blocked, I plan to retrofit it to R134a. It has been previously charged with R413 (as here you don't find R12) which is in Europe the best solution if you don't retrofit (but most expensive: about $200 for upload at an A/C automotive specialist).
Shall I discharge securely this R413 by myself (and how) as the compressor is completely blocked, the clutch blown away, and my Explo blocked in front of my garage door with a bad A/C belt??? (headaches: I don't want to burn away the old bet and destroy engine, but I don't neither wanna use the brand new I've just bought from Ford...)
I will change compressor, clutch, filter, valve and evaporator, then replace the belt and go to the next equipped garage to have a vacuum and reload...
what a program!
Thanks for you reply, Olivier

Indeed, V8's justification is sound, but on my '93 Ranger, it boiled down to dollars and cents: Let's weigh the options: a $700 rebuild that may or may not hold a charge for the summer, or a $30 conversion that may or may not last through the summer? If the $700 rebuild doesn't last, I'm out at least another $150 in R-12 to get it fixed. If the R-134 doesn't last, I'm only out another $30 on top of the conversion.... I took my chances, and it was well-worth the investment. I had a leaky replacement schraeder valve two days after the "conversion". The shop I bought it from threw in the replacement R-134 for the second re-charge because the valve failed. It ran for three more years without a problem after that.

Preach all you want about the "right" way to do it, and from a mechanical standpoint, I'll agree with you 100%. But at the same time I'll swear by the conversions every time. The benefit doesn't justify the cost for me.

-Joe

by the way, could someone tell me how much R134a I have to charge once retrofitted? Prevoiusly, it was 0.750 kg R12 (said on the label...)

Around here some people drive south of the border into Mexico where R12 is inexpensive. Are there any countries near you where you could get the work done cheaper? Going south for some surfing, lobster and R12 makes a pretty good weekend.
:thumbsup:

On a conversion it is not a bad idea to start with 75-80% of the R-12 charge when converting to 134 and start checking vent temps and presures then go from there. Some will tell you add 60%, others say add 80% etc... 75% is a good start and feel your way along from there is my advice.

gijoe, I am not in disagreement with you. I apologize for sounding "preachy".

You didn't sound preachy.... well, maybe just a little bit at first. I can't argue your point about the mechanics as you are 100% correct and I'm 100% in agreement with you on it being the true "right way" to do it. I found a fairly successful alternative that worked for me and, while it's not exactly "according to Hoyle," it may help others in choosing the best option for them. I make a fairly decent living, but I'd be hard-pressed to fork over $600+ when a $30 fix might work almost as well. Sure, it might not work quite as well as the total retrofit, but for $30 on a car that's only worth $3000, it sounds like a decent enough deal. I also looked at it this way.... sure it's not as efficient as a full conversion or as the R-12 it replaced was. Say it only works 70% as well as the R-12 system.... that's only a 30% reduction in efficiency, and still a full 70% better than it was working after it failed. :) Again, for $30, it's worth a shot, for sure.

I certainly wasn't looking to pick a fight or anything either.... Just sharing my opinion on the matter too. :) :chug: :chug:

-Joe

No offense taken. Sharing honest intelligently thought out opinions is what makes this board such a great place. You have already established your credentials in my book as someone who knows his stuff. Thanks for adding to this thread. You point of view is certainly a valid one!

my ac was retro to 134.my problem is my husband change the ofice tube.now my dryer freezes up and he says my low pressurer is very high and the compressor doesnt cycles off.but on a hot day my temp threw the vents runs about 50 degrees.he is going to replace the cycle swithch and add a little more r134.is this a good idea.

when you say your dryer is freezing I am assuming you mean your evaporator. The low rpessure cutout switch is designed to prevent this by cutting off the compressor when the low side pressure gets to a oint where the evap temps could cause it to freeze. Replacing this switch is a good idea if your low side gets below 25-27 psi and the compressor continues to run. Not sure what he means when he says low side pressures are high.... since refrigerant pressure has an equivalent temperature, high pressures in the low side of the system would not be likely to produce temps sufficient to freeze your evaporator. I doubt your low side is high, I suspect the cycling (low pressure cutout) switch is your main culprit. From here I cannot really comment on the charge state.

******AC noob question alert****

how can I check to see where exactly my system is leaking? I know my way around the garage/toolbox but I have never worked on a AC system

thanks

Sometimes you will see an oily stain around a leaking fitting, but not usually. You can either add UV dye to the system and check it with a blacklight, or use an electronic halogen detector (I refer to these as sniffers). You can also use an old style "sniffer" which used a propane torch (color of flame changes). Best and fastest? Sniffer, easiest ? blacklight.

Check your accumulator, these had a tendency to rust under the styrofoam "blanket" and leak. Make sure you have caps on the high and low side fittings.

Good thread. Interestingly, I have not seen the proper low-side psi numbers for an R-134a-equipped a/c system in this thread. Maybe I have missed it?

I also have a question re: my truck's a/c, and I think this is as good a place as any to ask it.

1) Is the low-side pressure the same for *ALL* R-134a systems, no matter the vehicle?

2) My truck is down to about 20 psi on the low-pressure side compressor off, when idling, doors open, a/c on max. Cycling seems normal to me, and during the compressor ON cycle the psi rises past 30 psi, but then drops to 20. The lines are not very cold, just cool to the touch. On an ambient air of 82 degF the system could only generate 54 degF air, even driving at 70 mph. My understanding is that I should be seeing 40 to 45 degreeF air on such a day. I conclude that I am due for a R-134a charge. Is this correct thinking?

On a fixed orifice valve system such as FORD uses, the low side will draw down as the compressor operates. Since pressure equates to temperature, to avoid freezing the evaporator, the system has a low side cutout that stops the compressor operation when the low side falls to that predetermined point (around 25-27 PSI.) The system off, high side and low side start towards each other, equalizing until the low side is high enough to allow the system to commence operations again. The cycles continue, their frequency based on a number of factors. On - Off - ON - Off.


If you find your compressor is cycling frequently, it is a good sign you may be low on refrigerant charge - it doesn't take long for the compressor to move out the refrigerant since it's low, and the low side comes down pretty quickly, hence the quick on/off cycle times. In a properly charged system you should expect 1-2 cycles per MINUTE. (Summertime temps of say 80 to 85 degrees outside).

High side in such a system will have pressures that vary, depending on condensor efficiency, airflow, ambient temp etc. In other words it's not like putting or checking air in a bicycle. They will vary. There is no absolute "right" pressure.


Hope this helps.

Yes, it does help, thank you a lot. I was aware of the basic operation of the system but you can never learn too much :) . I believe I'm getting at least 4-5 cycles per minute and the tubes are not as cold as they should be.

My understanding is that the thicker tube leading back to the compressor should be a little colder than the thinner tube. Neither of them are as cold as they should be.

Is an R-134a system a "closed" system? In other words, assuming all the o-rings and seals are working, no refrigerant should be escaping, if it's truly closed. Therefore, how can the R-134a need charging UNLESS it is leaking? Or does the refrigerant simply deteriorate/break down over time? If it deteriorates, what is it replaced with, plain air?

Rhett,

The thick tube is the "low side" and will be cold, the thin tube is the "high side" and will be warm/hot.

The A/C system is indeed closed, and you have a leak. It could be as simple as your service port valves.

As V-8 indicates the system is closed. However there are a multiplicity of seals and O-rings, and two valve ports, all of which can leak... add changing heat and motion and vibratin and you can more or less guarantee SOME leakage. the R-134 molecule is extraordinarily small. Anyway, I think it fair to say that "some" leakage over time is more or less inevitable. (in contrast the r-12 molecule is MUCH larger and hence less prone to leakage, but still will.)

Thank you both for the info. I will re-charge the system and it SHOULD take care of things, unless there is a significant leak. I have owned this truck for 5 years now and have never had to charge it so it's probably due for a charge.

I have a can of R-134a, a hose, and pressure gauge, but I don't have the valve that you spear into the R-134a can to open it. Guess I'll be going to the parts store to get that this evening.

I just to add my 2 bits about not being able to pull a hard vacuum. If I cant get a good solid 29 in hg vacuun or better I finially fill with one can of refridgerant. Then after I think it has mixed I pull another vacuum thinking that whatever air was not evacuated from the first pull will mix and be removed from the second. Seems to work pretty good.
During my past life as an engineer I did the math to compute how good this method would be for other gasses we were working with. Turns out the math told the truth when we did gas concentration measurments. A really good vacuum pump is still best, but this workaround seems to work.
Jerry

Glacier...any advice on how do "dial in" an A/C system? Add/remove refridgerant until a certain # of cycles per minute? Add/remove until a certain temp in the ducts? Add/remove until ???...I'm all ears.

Dave I am not sure I can answer this question as well as you might like me to but let me try.

Let's start with the two extremes. A) Not enough refrigerant, and B) too much refrigerant. If the refrigerant is low, the clutch will cycle out (e.g. turn the compressor off), and the refrigerant at the evaporator will expand and warm up before it is fully through the evaporator, leading to inadequate cooling. If the refrigerant charge is too high, the refrigerant will not have fully expanded by the time it gets across the evaporator, wasting cooling capacity. (This can also be bad for the compressor as it might be trying to compress liquid - sometimes called a flooded evaparator). The ideal is somewhere in between.

Put another more technical way - the inlet and outlet of the evaporator should be between 5 to 10 degrees or so apart (representing the superheat of the system... superheat is a concept based on physics and the latent heat of vaporization and latent heat of condensation - not super complicated concept yet not worthy of the time and space here).

Ok, that out of the way, here is what I could recommend where you have a system needing refrigerant - with enough to run the system yet not adequately cool it... Run the engine and start the AC. I'd prefer cabin temps be 70-75 degrees, and I'd have you put a fan in front of the condensor to aid in heat removal. Maybe even squirt the condensor with a hose a few times to help get things stabilized). Monitor your vent temps - increase the engine rpm to 1500 and keep it there for the duration of this procedure. After 5-10 minutes you can start. Add refrigerant until your vent temps head down... slow down a bit and continue to add about 3-4 oz at a time until the vent temps fail to go any lower. Then ...Add another 2-3 oz and see if the temps increase, if not, call it good. If so, bleed that back off and leave it as is.

It is a little easier to do this with equipment that lets you weigh the jug as you go (to 1/4 of an oz.) and will also recover excess charge.

Alternatively, to be able to recover the full charge and separate the oil is heaven, because then you can put in the exact factory charge and know where you are on oil as well... but then... that means taking it to a shop as a general rule.

Anyway, this is not an exact science, but that's my answer. Hope that helps. Stabilize the lowest vent temps is the short answer.

Chris gave me the "add untill the vent temps stabilize" advice two years ago when I re-did the A/C on my truck, and it worked extremely well.

I was able to acheive vent temps of 40.5 degrees on a 76 degree day, high side 190psi, low side 30psi. I added about 27 ounces of R134 to an evacuated system. The plaque in the engine bay said 30 ounces. FWIW.

Read more here: http://www.explorerforum.com/forums/showthread.php?s=&postid=667436#post667436

I've given directions to this thread about 20 times in the past month, maybe I should just bump it.

Glacier -- on my '00 the shrader valves are leaking on my 134A- system and we were going to go replace them, but good lord --- those things are huge. I called auto zone and Advance to see if they had the tool, but they don't. I am getting the shop to order one, but I was wondering if you'd ever come across these huge shrader valves. Oh, and don't worry - we evacuated the system so it's bone dry. 100% 134A and 0.0 Air.

-Drew

Yeah, you are talking about the larger cores... early 134's were using the same cores as the R-12's some switched over to larger "JRA-Eaton" cores..... and they ARE big.

They cost about $6 ea. As for the tool.... AC SOurce is a great supplier and here's their tool:

http://www.acsource.com/index.asp?PageAction=VIEWPROD&ProdID=281

Good luck. Mineral oil is a great lube for this btw.

I believe we have the shrader valves at work, we just didn't have the tool to remove them. Thanks for the link.

-Drew

must be a early 94 explorer! my 94xlt has 134, but makes no difference to me. my compressor is out! :( its going to cost a fortune to get it repaired! so i go to old cooling method! 65mph 4 windows down! lol

I got the right tool from the Snap-On guy. He came by today (friday) and he went on a run for me to get it. The shop paid for it, so I don't know how much it was. :thumbsup: Anyway, got the shrader valves out, both different sizes and then pulled a vaccum on the system for 45 minutes and then recharged the system with 1.8 lbs and added some uv dye. The valves didnt' seem to be leaking - atleast they weren't whistling at me like the other ones. I got a cool 40 degrees on only a 8 minutes drive with max a/c and high fan -- it was around 85 degrees outside. I have a temp gauge in there right now, but I will take a longer drive tomorrow or Sunday. Thanks for the info Glacier.

-Drew

2006 and it is time again to turn our attention to AC issues.

I have a '93 that was converted to 134 by the previous owner's mechanic. No way to know if the O-tube was changed.

But I haven't been able to get lower temps than about 50 at the center vent, hi speed, whether by raising or lowering the amount of 134 in the system.

I'm looking at the original condenser and thinking about switching it with a parallel model. I did this successfully with a '90 Camry; it means hose work and some fabrication of brackets.

Has anyone here done it on an Ex? If so, what did you learn?

EDIT: Found my answer here (http://www.autoacforum.com/messageview.cfm?catid=2&threadid=15368&FTVAR_MSGDBTABLE=).

OK, I started a thread about replacing the Evaporator core http://www.explorerforum.com/forums/showthread.php?p=1697094#post1697094 but I have a couple questions about parts and this thread is the most comprehensive of the 50 I have read.

? NYLOG lube, what color for the HNBR (green) O rings? (I saw it in one of the 50 threads but can't find the thread again)

? AC Kits shows 2 orifice tubes, Blue and Red, which one for a '94



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Beside, it's that time of year so BUMP

i read the first post in this thread and found the link to be a deadlink....update??

Glacier...any advice on how do "dial in" an A/C system? Add/remove refridgerant until a certain # of cycles per minute? Add/remove until a certain temp in the ducts? Add/remove until ???...I'm all ears.

I'm not Glacier, but I wish I had his tool kit. :p:

One technique that old pros swear by is to add refrigerant until the pipe going into the evaporator is about the same temperature as the pipe going out.

Some do it by feel, but it's better to use a probe of some sort.

Here is a guy who did a conversion, on his '93 Explorer, R-12 to R-134........

A Job Well Done.......I might add......

http://www.explorerforum.com/forums/showthread.php?t=192983

Aloha, Mark


PS..........OK, I started a thread about replacing the Evaporator core http://www.explorerforum.com/forums/...94#post1697094 but I have a couple questions about parts and this thread is the most comprehensive of the 50 I have read.

? NYLOG lube, what color for the HNBR (green) O rings? (I saw it in one of the 50 threads but can't find the thread again)

? AC Kits shows 2 orifice tubes, Blue and Red, which one for a '94

The Nylog color is BLUE (for green O rings, R-134a and PAG 100 oil in you FORD Explorer conversion).

http://www.refrigtech.com/nylogmanual1.html

Orifice Tube for a stock '94 Explorer A/C system w/ R-134a, is BLUE.

IF I was doing a conversion of a '91-93, I'd go with the BLUE orifice tube.......see WHY (IMHO) in the link (in my post #99).

...I thought I would throw this in here as it has become available out here as the replacement to R-12...

...You have to call around to different auto parts and ask for freeze 12...;)

...Link to their info...
http://www.freeze12.com/

http://www.explorerforum.com/photopost/data/500/misc_0112.jpg

Have you used Freeze 12? I wonder how good it really is?

I need to recharge my A/C - I have 3 cans of R-12, but I only have 3 cans.

If you know a carrier I can ship it with, I have a case of R-12.

Have you used Freeze 12? I wonder how good it really is?

I need to recharge my A/C - I have 3 cans of R-12, but I only have 3 cans.

...I have the freeze12 in my X...My mechanic buddy uses it in all the R 12 vehicles now..:dunno:

..Mind you, he did a full service on the A/C when he installed it...

I had a mechanic put 134a on top of r12 without converting anything, he did nothing but hook on to my system and added the 134a, a few days later the system quit cooling and i took it to another mechanic where he said my system is ruined and that i would have to replace the whole ac system now, is this true and if so is the certified licensed mechanic responsible for this.....

Okieplayer, whether the technician who added R134 to your system is responsible (leagally) or not is dependent on what state you reside in. You can contact the better business bureau of your state and check with them. You can also check with the DMV in your state and find out if there are any consumer protection organizations that can assist you. If you happen to be in California, We have the Bureau of Automotive Repair. You can file a complaint with the BAR and they will look into the facts of your complaint and attempt to determine fault and if determined to be in your favor, they will attempt to secure a refund or rework of the repairs.

I am getting ready to do a conversion of my 92 xlt ranger. I will be replacing the compressor, accumulator, orifice tube and main hose from compressor to condenser and accumulator.

Can anyone tell me how much oil I should add to the accumulator, the condenser, and the evaporator?

Should I use PAG oil?

What would be the correct amount of R134 freon to use. (intend to have the unit recharged at a local shop, but they wont do it unless I can tell them how much to put in).

Finally, Do I need to remove the condenser to properly flush it?

Thanks for any help.