How to: Converting an R-12 Air Conditioner to use R-134a

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. 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.

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??

85Dave said:

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.

Click to expand...

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

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

Click to expand...

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/