I decided to start my own thread to try and diagnose/fix my A/C system.

Symptoms:
When put on Max AC, A/C system will cycle on for 2 seconds, then shut off for 10, then go on for 2....

Ambient Air temp: 80 degrees, Low side pressure: 30psi High side pressure: 100psi. I did the "5 seconds charge test" (depress low side valve for 5 seconds, listen for constant or petering out hiss) - and it passed with a constant hiss.

I tried to add a can of 134a, and the system behaved the same - it didn't want to take the can.

I can hear the low pressure switch clicking on and off with the system - I'm thinking that it, or the high pressure switch may be defective.

Is there any way to test the switches? I was thinking my air compressor.....

Let me know what you think

I went ahead and purchased a new cycling switch (the one on the accumulator near the low side port) for $15.

Still the same problem, the 2 second cycling on/off. It appears to be pressure related, with the fresh can of 134 disconnected, the pressures are as follows (85 deg amb)
Low side: On=35 Off=40
High Side: On=115 Off=110

The sytem is cyling pretty fast now.

When I open the can of 134 into the low side, the low side pressure stabilizes at around 70 - but the cycling continues.

I put a manual push button switch inplace of the cylcing switch. Sure enough, the Low side pressures went down to at least 10psi before i cut it out. I'm trying to add 134a as we speak.

Ok.... More diagnostics:
Using my new pushbutton, I put in the can of 134a. I dipped the 12oz can in hot water - it emptied pretty quick. Now I'm getting weirder results. When I reconnect the cycling switch, it still does the "on 2, off 2" routine. However - the pressures don't change, and are as follows: Low 106 psi, High 100 <<Those are not typos, the low is higher than the high! Its most likely

I'm thinking a blockage somewhere, say orifice tube or accumulator. But I'd hate to tear into the system.

Any thoughts? I know this is a lot here, but hopefully someone can help me shed some light onto my problem.

What am I doing wrong?

When you check the pressure on the low side does it jump from nothing to way high back to nothing as the compressor cycles on and off?

If this is happening then you are low on 134a and probably have a leak somewhere. As posted on the other AC thread the accumulator rusts out and needs to be replaced on this X. You probably need a new one like mine did.

Under that foam cover is a bunch of rust which is caused by the foam cover holding water against the accumulator.

Good Luck,
mikeh

Mike - thanks for the heads up, it reminds me: I was reading another thread about A/C and someone said that they found a leak in the accumulator behind the foam. It will be my next step to check, but tomorrow I get my wisdom teeth yanked so my Mountaineer will have to wait. :(

V8...

I'd be suspicious of either a blocked expansion valve, or a compressor problem. The system itself is pretty easy ... expansion valve, low side pressure switch, overpressure cutout on high side and the compressor about comprise it. I fear that recovering the refrigerant and opening it up and seeing what you find may be your only chance to diagnose it. Your numbers do NOT sound good. A blocked expansion tube usually means system failure. I hate to tell you my gut feeling on this one.

Happy exploring...

Chris

Chris - thanks for jumping in on my thread.

I'm determined to get this system working, i purchased the truck in the winter knowing the A/C was bad, and got one heck of a deal. I'm doing most of the work myself, doesn't matter what.

If you where here to work on the truck with me, what would your next step be? I'm going to evacuate the system as a first step. Then remove the orifice tube to check for black death. Keeping my fingers crossed, I'll post photos of what I find.

After I posted, I took the manifold off of the truck and I think they may have been wrong. The pressues I posted above may be due to me be being funky with the manifold valves and hoses. We'll see - it would be great if it is just the accumulator, o-tube and a flush.

What is your opinion on AC components such as O-tubes and accumulators from Autozone, Pepboys, etc. I know the guys on www.aircondition.com despise them. If it does turn out to be a compressor, then OEM is the only way I'd go.

While it's open, what do you think about replacing the valve cores? How is this done? I did some searches at www.aircondition.com and they seem to think that Explorer failures are due to 1) accumulator blanket 2)
valve cores 3) compressor front seal

Opinions?

Thanks,
Aaron

V8 -

Let's start methodically without jumping into opening it up until we have some concrete ideas of pressures. Try again hooking up your manifold (and don't feel bad I HATE the newer setup used on 134a systems with all their backflow prevention stuff and all). Get hi/low pressures and ambient temp, and if it is cooling at ALL, vent temps. describe your readings once you are confident you are getting an accurate read. Let's go from there.

We can talk schrader valves and all that once we decide, and if we decide, to open er up.


Happy exploring


Chris

Chris,

After a delay due to getting my widsom teeth out, I'm back and ready to solve this A/C problem. I went out to the truck today and found some interesting things.

1) I removed the foam from around the accumulator. WHOA. Inside was a mess of rust, what appeared to be oil, 134, and some UV dye. I'm betting this thing is leaking.

2) I hooked up the manifold after working out my backflow valve issues. Here is what I found:
Ambient Temp: 60 degrees (This NE weather is crazy)
P static: 76psi
P on: Low=25 before cut off
High=100

The system had its usual 2 sec cycling.

I tried to add gas from a can at amb temp, and the low side held at around 60, the high fluctuated around 100. The system continued to cycle, but the cycles were longer. I didn't bother jumping the cycling switch this time. I chose not to add that much gas, I merely wanted to see the system's response.

I'm thinking its time to open her up and buy some components. Let me know.

Thanks for all your help
-Aaron

Aaron...

Now those pressures make some sense <g>. Your low cutout is kicking in at 25, which is about right. When you connect your can to the low side the pressure jumps to near static, which is to be expected. The low high side pressure is due to either insufficient refrigerant (probable) or a bad compressor (not impossible but a less likely 2nd choice). If your receiver/dryer/accumulator is as you say, it would be good to replace it. Add a couple ounces of oil to it. You are probably PAG oil, the sticker in the engine compartment should say. As long as you are discharged and open, be a good idea to take a look at the expansion valve. You will in all liklihood need a puller for that, and you can borrow or buy one at Autozone.

Assuming the expansion valve is ok, if it were me, I'd pull a good vacuum on the system and recharge it with the factory amount of R-134 and see what gives.

If the expansion valve is sooty and crudded, well, then we have another issue. As for the schrader valves, I'm not sure from what you are saying that they are a problem. You may just want to leave them alone.

Keep us posted on your progress.

Tomorrow after work I'm picking up a new Accumulator and orifice tube. I'm using new Motorcraft parts. It will be interesting to see the condition of the inside of the system.

When I'm re-building:
1) How much oil should I put back into the system? Is it necessary to use ford OEM oil, or will any PAG do it?

2) Do you recommend adding a Dye to the refrigerant?

3) I've read about "smart" orifice tubes, or Variable Orfice Valves "VOV." Are these things worth it, or a gimmick?

Thanks,
Aaron

Aaron... (assuming your system is PAG oil) any PAG is fine, certainly nothing wrong with picking it up while you at your Ford store. As for Dye, that's an individual call. I hear some claim is has a long term adverse effect, others say that's hogwash. Genetech is even offering R-134 with dye already in it! It's a cheap way for a DIY'er to find leaks, so your call. VOV are reasonably new, and make claims of improved cooling at idle. Some think one more moving part is one more moving part too many. I have no experience with them to be able to answer your Q. As for oil, I'd ordinarily add an ounce to an ounce and a half to a receiver/dryer/accumulator when I replace it. You mentioned seeing some oil around what you suspect was the leak, so I upped it to 2 ounces. Just pour it into the unit before you install it.

Good luck.

Happy exploring

Chris

This is a copy of the original writeup: http://www.explorerforum.com/forums/showthread.php?s=&postid=667436#post667436 I may update the main post, please check there for new thoughts.

I purchased the truck in the winter knowing the A/C wasn't working. Even on warm days, the compressor would cycle on for a few seconds and then shut off for ten. Pressures were low.
http://www.ackits.com/blackdeath/airprobdimage/system.gif
Diagram of A/C system, courtesy of www.ackits.com

Daignostics
On 1996-1998 V8 Explorers and Mountaineers, Ford wrapped the accumulator with a foam blanket. My guess is they figured since the accumulator is in the low side (hoses are cold) and it is right over the passenger exhaust manifold, they wanted to insulate it. However, the accumulator sweats, the foam trapped in the moisture and the steel rusted.
http://www.explorerforum.com/data/2/13422accumulator_comparison.jpg
Comparison of New and Old Accumulators

After peeling away the foam, I found a mess of rust, PAG oil, and flourescent dye. (Ford adds dye in the factory) A new Motorcraft Accumulator was $65.

Repair
The system was discharged, and the accumulator removed. One of the fittings is a simple hex nut, the other is a spring disconnect. The spring disconnect tool is also used on the fuel system, and can be purchased at Autozone for less than $10.

While the system was open, I wanted to inspect and change the orifice tube. Located in the inlet to the evaporator (the one that get's cold, near the dash). It is a filter/metering valve.
http://www.explorerforum.com/data/2/13422o_tube.jpg
Old Orifice Tube, 109,500mi

Often times the orifice tube is an excellent indicator of system health. If a compressor is going, little metal fragments will start to clog up the screen. If the compressor is gone, "black death" will load up the orifice tube with gunk. http://www.ackits.com/index.cfm?fuseaction=Black%20Death

My orifice tube was fine, and did not need replacement. However, since the system was open, the tube was out, and a new Motorcraft OEM tube was $4.00, a new one was installed. A special puller is needed to remove/insert the o-tube, I "rented" one from Autozone for free.

When assembling the system, the o-ring seals were dipped in the air conditioning oil, PAG 46. 2.25 oz of PAG were also added to the accumulator before it was reassembled to replace lost oil. The Cycling switch was re-attached to the accumulator.

Evacuation
After the system was buttoned up, a vacuum was pulled. This is where the difficulty was. A/C systems MUST be vaccumed to remove air. The vacuuming accomplishes two things: 1) It removes air from the system. When expanding, air does not get cold like 134a, yet has volume, reducing cooling capacity. 2) A vacuum will lower the boiling point of water(moisture). Moisture in the A/C system can form acid.

The ideal vacuum pump is a dedicated electric refrigeration pump, capable of pulling down to 50 microns, or 29.9 in Hg. No one in the Boston area rented them, they cost $200. I had used a ventrui effect air-driven vacuum pump on two previous R12-R134a conversions, which cost me $30.
http://www.explorerforum.com/data/2/13422air_vac.jpg
Robinair Air-Vac

The the AirVac however did not pull past 26inHg. My medium sized compressor (5hp, 5.1scfm@90psi, 22gal) could not keep up with the 90psi the AirVac's needs. I held the 26in HG vacuum for about 1 hour, with the Air_Vac running. I cycled it on/off not to strain my compressor. I wasn't too worried about moisture since the system was open for less then 30min, on a very dry day. The excess air, would mean higher vent temps. Oh Well. I have since heard that the pull to 26inHG is almost instant, but the AirVac can pull to 29.7in HG if given enough time.
EDIT:Many people who use these make a manifold to run two compressors, to maintain constant high pressure and not damage the compressors. Also, I've heard that it is possible to make a vacuum pump from an old compressor (Refigerator, dehumidifier, window A/C). I may look into this, there a window unit from the 70s in our basement)

Charging
With the engine off, the first 12oz can of 134a was discharged into the system's high and low side upside down as a liquid. The can emptied 100%. A second can was attached, right side up. The high side valve was closed, and the engine started. The A/C control was on "Max A/C," the temp all the way cold, and the fan on max. All windows/sunroof were open.
http://www.explorerforum.com/data/2/13422manifold.jpg
Gauge Manifold

Charging was done using the temperature probe of my Mac Tools 710 Digital Multimeter. Very accurate, it's remote probe reads in tenths of a degree. I added gas untill the vent temps settled on 40.5 deg F. The Ambient temperature was 76 degrees, High side pressure was 190psi, Low side pressure was 30 psi. Adding gas took a VERY long time, almost 30 minutes. I've heard people say that you can dip the can of 134 into hot water to speed of the process, but others say not too. I chose to take it slow and easy. You can see when the clutch cycles by the increase/decrease in vent temp. Often the difference will be by 3 degrees. As the system nears full capacity, the cycling will stop, and vent temps will remain constant. The sticker on the dash says the system will hold 1 lb 14 oz of R134. This is 30 oz, exactly equal to 2.5 12 oz cans of R134. I estimate I was able to add about 26-27 oz of R134, leaving about 3oz of air in the system.

The clutch does not cycle often now, and the air is nice and chilled! Special thanks go out to Chris, Glacier991, who gave me advice along the way.

Originally posted by V8BoatBuilder
Special thanks go out to Chris, Glacier991, who gave me advice along the way.

Nice writeup V8BB. But no thanks for me when I described your problem to a tee?:mad: :mad:

Come on I want my props.:D :D

I wish I had the equipment to do this one myself. It cost me $300 at the dealer. What was your final cost including tools that you had to buy? I guess it wouldn't have saved me too much. It's just that I hate to take the truck to dealer.

mikeh

Awesome write-up with pics. Great post.

Lou.

Mike - you definitley hit my problem right on! So i'll give you some props ;)

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

As for the tools, lets see:

1) Gauge Manifold/Hose Set: $60 (Got a great deal!)
2) Vaccum Pump: $30 (Though if i had to do it over, I may have bought a used electric rather than the venturi. But I had shop air)
3) Orifice tube remover: Rented free
4) Digital themometer: Part of my multimeter, which I use as often as a screwdriver!
5) General sockets, wrenches... yada yada...

That's about it. I bought the gauges/hoses and pump last year and did two "Wal-mart" a/c conversions on two Peugeots. So the set has been used on 3 vehicles so far, not bad.

As for the cost of the repair:
1) Motorcraft OEM accumulator: $65 (I could have had a cheapie knockoff for as little as $45.)
2) Motorcraft Orifice Tube: $4.00 (Not needed, but worth replacing while system was open)
3) PAG 46 oil: $5.00 8oz bottle
4) 3 cans R134a: $1.99/ea (got a LOT at a sale a year ago.... had a hunch)

My hat is off to V8. I believe that a DIY CAN do A/C so long as they realize the issues and problems and act accordingly, not just dump in a "kit" and think they aced it. His post with pics was terrific and was what I hoped to have people here realize. YOU can do it, but BUY a gauge set fer chrissakes. I could add to his list but it's a good one. I'd add eye protection, but of course that is not a tool. just a MUST HAVE. If you are a DIY, read his post carefully. THAT is how you SHOULD do it.

Great work V8.


Happy exploring


Chris

Chris is right about the eye protection - I've heard that a stray shot of 134a in the eye can cause blindness. I have a nice set of goggles from my school's chemistry department ;)

I also should add can tap/valves to my list of things above, I had several from the "Death kit" conversions I did.

I chose not to add dye to the system (see earlier post). There was dye in the system from the factory, and there appeared to be residual amounts left in the system after it was recharged. If the system develops a leak, I will add dye then or just use a sniffer to find the leak. A/C systems are so fragile, why put added stress on an already weak compressor.

Well I finally have a nice and hot day to test out my A/C, here are the results:

Ambinet temp: 83 degrees
Vent Temp: 49 degrees.

The above was taken with the engine at idle speed. Cooling was noticably better when the truck was moving.

Temp reading taken from center A/C vent, controls on max fan, max a/c, doors/roof open.

I'm not sure if that's "good" or "bad" compared to other Explorers, but it sure feels great!

great write-up.

I just found the ac problem on my '97 today...took my local guy five minutes to find a vacuum line that "Ford" had incorrectly installed last year when they replaced my intake manifold. Yep, I went all last summer with no ac because of the dealership.

I'm gonna go check the Accumulator though as I'm sure mine is rusty and quite possibly leaking as well.

Thanks again!

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

How much do you think a shop will charge to install a new accumulator? Do you have to vacum out everything? How tough is that to do?

The accumulator will run you $75 to $100 depending. The remove and reinstall will be about .5 hours of shop time. The system will need to be evacuated and recharged. Charge for that varies with refrigerant between $125 and $200 would be my guess. HTH.


Happy Exploring

Chris

I was reading in the haynes manual abouth the removal and install of the accumulator. It says to take your truck to a shop to get the a/c system discharged by a shop. Then install your new accumulator, then go back to the same shop for the recharge. So, will most shops discharge an a/c? I will want to install the accumulator myself, then recharge it myself using my "at home r134 kit" How does this sound? What will a shop charge? It shouldn't take very long for them to do it?
Thanks Guys
Brian

Brian.... answers to most of your questions are already in this thread. In an earlier post you mentioned "vacuuming out" like it's simply a matter of sucking out old stuff... it's not. You have to establish a very good vacuum within the closed A/C system before you reintroduce the new refrigerant - that means attaching a vacuum pump and running it a while! V8BoatBuilder used an air powered vacuum pump and got decent results, but I think if he had his choice he would have rather used an electric vacuum pump. He also had a gauge set. Both of those are very important things to have. I think his post is excellent and provides a good step by step "how to". Can you do it with less ? Probably. Will it work as well. No.

Happy Exploring

Chris

In my case, being a DIY A/C technician means not being the best citizen for the environment. Most of the refrigerant in the system had already leaked out through the rusty accumulator, I went ahead and vented the rest. R134a isn't as bad for the ozone as R12. While I wish I could have recovered it, it just wasn't feasbile.

If your system is almost dry, then releasing a few ounces of R134a probubly isn't that bad. Not great though. Releasing a full system to change a component, that's a tough call - I don't think I'd do it.

When you release the refrigerant, air will enter the system and the system will be at zero psi. Not pressurized, not a vacuum, but still "full" of air. The system is vacuumed so that it is truly empty. Any air remaining will decrease system effectiveness. I was not able to get all of the air out - though I got most :)

I used a venturi pump on my air compressor. It worked - I can sit in 90 degree heat, in the sun, with a black car, in stop and go traffic, and be so cold I have to turn up the thermostat. However, I've found that all windows and the roof must be closed and the control on "Max A/C" otherwise it just can't keep up. I couldn't find an electric vacuum pump to rent or buy cheap enough. But - if I had one to use, it would have been a no brainer.

I'm gonna bring up an old thread here but I'm curious where I need to vent the system? I'm thinking of replacing the compressor in a friends X. How different are these steps for the accumulator from the steps I would need for the compressor?

Awesome thread. I'm just about to start working on my A/C system. I had it discharged at a local shop before doing the engine swap. Even though they charged me $50 I thought it was better than putting it into the atmosphere.

Anyhow I have a venturi pump just like V8boatbuilder and I too can only get about 25 ~ 26 hg and I have a pretty decent compressor. It stands taller than I do, runs on 220, and moves about 12 CFM at 90 PSI all day long without breaking a sweat. I normally use it for sand blasting. I'd like to purchase a real electric vacuum pump as I do tinker with A/C systems from time to time.

I already have a manifold gauge set and an electronic leak detector.

My questions are :)
1) Where is a good place to get an electric vacuum pump?
2) How do flush or clean the system out first? I've had it open for about 2 months and been driving it for about 2 weeks. I assume there's dust or other dirt I need to blow out with the air compressor and some solvent. But which solvent? Or does it not matter?
3) How much pag oil do I add to an open system? This is a 94 Ranger originally with the 4.0 V6 now running the 302 from a 2000 Explorer. Compressors look the same and I'm using all the other original Ranger A/C parts which look pretty much the same.
4) Are there any official specs as to what the pressures should be on the high and low side when I charge the system?

Thanks for any info
Malcolm

I hope someone will correct me if I'm wrong but for question #2 I believe I read in another AC post that some have used brake fluid?

Brake fluid? wow I don't know. That would be very hard to get out. I was thinking of something more like acetone or any other solvent that will evaporate at room temperature. Seems like brake fluid would leave an oily residue? But I don't know, just guessing here.

First off, an electric vacuum pump can be had on E-bay for between $100 and $200. There is a "new" one for sale relatively cheaply... it seems a tad small HP wise, but claims to have a good drawdown vacuum number in the micron range...you may need to run it 45 mins or so, but it should be ok.... here's a link, you can also do a search on E-bay for vacuum pump
http://cgi.ebay.com/NEW-MOUNTAIN-1-5-CFM-A-C-VACUUM-PUMP_W0QQitemZ7558064888QQcategoryZ66999QQrdZ1QQcmdZViewItem

DO NOT USE BRAKE FLUID as flush. Brake cleaner maybe. I recommend you buy a quart of commercial flush and look into a flush gun, or borrow mine. It'll set you back $15 for the flush fluid. You also might want to change your Orifice tube.... I can send you one for 134a. I think they cost me about $3.

Since your system is empty, recharge by weight. Pressures will depend on too many variables to tell you much, and the low side pressure switch will be cutting out frequently if it is cool outside.

The quantity of R-134 should be 75-80% of the R-12 quantity. Oil should be the same (7 oz I think - spread it throughout the system). THAT data should be in your CD !

There is a long A/C thread in the Useful threads (Now in this forum as well)that should serve as a good educational tool for those curious about A/C. Although it is about converting to 134, it covers all the A/C bases.

I thought I was way off base but I just messed up the whole fluid and cleaner! :D Here is a quote from v8 boatbuilder:
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...

I got it from this post:Converting an R-12 Air Conditioner to use R-134a (http://www.explorerforum.com/forums/showthread.php?t=77331&highlight=AC+Conversion)

Thanks for all the info guys. I'll be buying a vacuum pump soon enough. Wow that one you linked to was only $124? They used to be much higher when I looked a few years ago.
Oh and FYI - my truck was R134a from the factory.
Glacier, I'll see if I can get the CDs loaded tonight. We're remodeling the inside of our house and it's a disaster right now :)

I have a question about this repair. I was always told that you should not have the A/C in MAX position when charging the A/C. The MAX position tends to pull cool air into the evaporator when warmer air is preferred which theorectically increases the systems ability to take in freon. Is this correct?

I think there might be a smidgen of rationale to that old wives tale....(more in terms of how quickly it will take the charge)...but, let me add my 2 cents worth.

If the system is empty, adding by weight is the best way to charge it. If you are topping off, you are going to want to try and fine tune the charge. Too little and you do not get cooling across the entire evaporator, and lose cooling capacity. Too much and you flood the evaporator, also losing cooling capacity.

I recommend fine tuning under real world conditions. That means if you are checking vent temps, you should try and simulate the actual operating conditions... fan on the cooler, and maybe AC set to MAX, if that is how you run it.

Actually, even though you DO recirculate cabin air in MAX A/C... which WOULD be cooler... the airflow is also higher... I bet the difference in heat removal in the evaporator is not all that great between the two unless the outside air is 90 degrees or higher.

Was that confusing enough for an answer ?

ps. Your question rather suggests a belief that the more refrigerant you can get into the system, the better. Not so. There is an optimal amount.... too much is bad, too little is not good either.