AC Conversion to R-134

Contributed By: Costas Papayanopoulos

I converted to R-134 last summer because one of my AC hoses had blown up the previous summer. Took the hose to the local machine shop and they made a new hose using the old fittings. By the way, the hose was too close to the exhaust manifold and showed signs of heat deterioration. I believe that caused the failure and that other GW's may suffer from the same problem!

MY EXPERIENCE

• Used a "front seal" kit for the York compressor and the cost was reasonable - about $20. You could get a rebuilt compressor for about $100, I believe.
• Replaced the receiver/drier. This was a PITA to do because of the drier's location behind the front grille, but it is a MUST. Just make sure the drier you get has either XH-7 or XH-9 desiccant. R-12 systems use XH-5 desiccant and this is not compatible with R-134a. I believe XH-5 is no longer in use but check just to make sure. Cost: $50.
• Removed ALL the old (mineral) oil from the compressor and replaced it with Ester oil. PAG is also acceptable but it more hydroscopic (i.e. will absorb moisture). In any case make sure that the oil container remains sealed until ready to use. I believe that replacing the drier and draining the compressor means that almost all the old oil is removed from the system. So, I added the full amount (7 oz.) of Ester oil to the compressor. I do not think that any oil needs to be added to the drier. A small amount always circulates with the refrigerant.
• Did NOT do anything about the expansion valve and that may have been a mistake.
• I also did NOT flush the system. Flushing is tricky because of the risk that some of the fluid that is used for flushing may remain in the system. The only method that I think makes sense involves too much work: All components must be removed and individually flushed and dried with DRY compressed air. I do not recall what the recommended flushing fluid is.
• Evacuated the system for 12 Hours(!). You only need to do this for about one hour normally but my system had been open for almost a year and some extra evacuation time does not hurt.
• Re-charged with 75% of refrigerant capacity, tested, then added more in 5% steps to 85%. The recommended maximum is 90% of the R-12 capacity because of the different properties of R-134a and R-12. I've several warnings against disregarding this limit!
• You can use any type of o-ring but you should lubricate it with a small amount of MINERAL (not Ester) oil before installation.

RESULTS

Not as good as I had hoped. The AC puts out a reasonable amount of cold air when the compressor is running but it seems that it cuts-out too often. Right now my theory is that I did not add a sufficient amount of refrigerant and that the system is shutting down because of low pressure. (There is a switch attached to the sight glass which I think is a low pressure switch).

Another problem was that while the original receiver/drier had a pressure relief valve, the replacement receiver/drier did not. (I assume that the EPA prohibits pressure relief valves these days). So my system is currently unprotected against a high-pressure condition (another reason why I added refrigerant very cautiously). I suppose I could try using a high-pressure switch wired in series with the low pressure one. Any comments on this would be appreciated!

MORE INFORMATION

I know that the EPA is not very popular with people who have AC problems but I found the following links to be useful and to the point:

The EPA's page on car and truck air conditioning:
http://www.epa.gov/ozone/title6/609/609.html

There are many links on this page. Here's some interesting ones:

Arctic Auto Air's Retrofit Procedures:
http://www.epa.gov/ozone/title6/609/oneshop.html

Guidance on R-134a Retrofits:
http://www.epa.gov/ozone/title6/609/retrguid.html