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
- 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
- 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
- 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.
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!
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:
There are many links on this page. Here's some interesting ones:
Arctic Auto Air's Retrofit Procedures:
Guidance on R-134a Retrofits:
Long Island, New York
"If your oil pressure is low and your blood
pressure is high you probably own a FSJ"