Over the last week, I have been converting my DOA R12 system to R-134a... I read through all the different postings here, and also consulting with a local car A/C shop I work with...

Here is what I did:
REPLACED:
Manifold Line
Liquid Line(links Evap/Orifice tube & condensor)
Orifice Tube
Accumulator/Receiver-dryer
Compressor
All O-rings (New GREEN ones)

I actually did part of the job TWICE- When I first got the new accumulator, I noticed it looked different from the OEM one. Not a little, but a lot. It looked like a capsule, where the original looked like a capped cylinder. At first I thought it might just be a manufacturer thing- But in place, it was just not a great fit. I carried on. I replaced the liquid line, and put a RED orifice tube in, replacing the blue one. All the o-rings were changed out, and a new pressure switch put on. I evacuated & charged the system(I do have a gauge set, but only have a crappy vacuum pump which works from compressed air line)

Anyway- Got it all evacuated, pulling around 26" for an hour, and charged the system. The compressor was only clicking in for a few seconds, and out again.(I had not replaced it at that point...) As it was fully charged, and not cycling properly, I decided to stop for the night, and check into what was going on.

I thought the problem had been with the cycling switch, as the R134 had different pressures I had been led to understand. So I went and got a switch for an R-134 system. It showed different pressures on that one, so I removed the R12 one(which promptly dropped behind the battery) and had hell trying to get the new one on. It kept blowing the o-ring out! SO I looked, and found the Schraeder valve extended PAST the end of the fitting! Something it did NOT do on the original accumulator. Tried a few things, nothing worked. Put the R12 one back on, and it DID go right on, minimum of trouble.

On the way home, I picked up another R-134 switch, as it appeared the one I had had stripped threads. I also looked at another accumulator, and found that another from the same company (4 seasons) with the same PN was almost identical to my OEM! So I bough another accumulator...

The next day, I talked with one of my students who is car A/C guy (not the shop I consult with) and when I mentioned I had NOT changed the compressor, he looked at me as if I had handed him a chicken painted bright orange and asked if I was nuts... We talked it over for a little bit, and I came to understand that the compressor was probably on its way out, so it would be best to replace it.

Over to Pep Boys, paid $31 to get the system evacuated & the refrigerant reclaimed(I do not have that equipment: evacuating an already empty system, no problem, removing freon, I need a shop) then back home. I replaced the compressor, and went to install one of the 105+ auto adjusting orifice tubes someone had recommended. When I pulled the orifice tube, I found it completely clogged with sludge! (This explains the VERY HIGH system readings I got when I checked it before evacuating the system)... Off to the A/C shop for a consult, and he told me to flush the condensor with liquid Brakekleen, then evacuate the system again. I did so- I cut the old hoses to give me a feed and a drain line, then fully filled the condensor with Brakekleen, as well as flushed the evaporator, and flushed through the line. I then blew it all out with shop air into a container, and got some nasty crud out. I kept blowingthrough each component until nothing came out.

Once all was cleaned out thoroughly, All new O-rings were once again installed, lightly lubed with PAG 46, the new compressor (New 4Seasons Ford FS10- not a rebuilt unit) SECOND new, but CORRECT Accumulator, the auto-adjust 105+ orifice tube & all the lines were reinstalled. I tried putting the new 134 cycling switch on, and realized the problem was there IS a thread difference between them! So I put the original R12 switch back on, and proceeded to evacuate & recharge the system...

I am VERY HAPPY to state she seems to work nicely! I am going to swing by the shop tomorrow for him to give it a quick check over, but think it is fine... It is a hair warmer than it calls for on the a/c thermometer (running about 50 when should be in 40s) but that could be because of conditions here, and not fully checking in shade, etc...

As the evaporator and condensor were the only things not replaced, I believe I have the right cure for the problem. As to the cycling switch, the SECOND 134 switch I got was marked with the SAME pressures as the R-12 one was! The first one was marked with slightly lower pressures. So- two of the SAME switch, yet two different settings... And the newer one matched the pressures for R12...

Lessons learned:
Replace the compressor- it will save trouble.
ALWAYS flush the condensor & evaporator.
R12 cycle switch ok for 134a.
If the accumulator in the box doesn't look right, send it back.

Sorry for the long post, but I hope it will help someone else considering converting to 134a. It WILL work- but YOU have to do the proper work first...

Scott
(Off to take a cool ride in the hot sun)

 

Glad you got it fixed. I decided to not do the conversion and just stick with the r12. My system was already empty. I've owned the truck 9 years and it's never blown cold. I found some r12a dye which is safe for R12 systems. Jumped the compressor and it sucked the dye right in. Later I found the source of the leak at the high pressure line. Fixed the leak. Recharged my system with r12a (again safe for R12 systems) by again jumping the compressor and adding r12a. I also added leak stop and more dye.

I know I didn't vacuum or convert but my ac blows cold and it really didn't take a lot of trouble or money. Most expensive part was the r12a.

Granted, I did get lucky in that I could find my leak and fix it. But not too many people know about this r12a and are under the impression they have to convert. This was kind of an experiment on my part to see if it would work and so far, so good!