Report on AC Conversion

Al Powell powellae at
Thu Sep 20 22:32:14 EDT 2001

Well, I've had my 1990 200 converted to R-134A for about a week now, and 
here's what I can report.

Short story - I had a shop vacuum the R-12 out of the system and remove the 
old compressor, then flush the system.  I installed the new compressor, dryer 
and orifice valve, then took it back to the shop to have them charge the 
system and install the needed oil.

Observations and notes about this procedure:

- You will have to scrounge for O-rings.  There are two on the dryer, one at 
the orifice valve connection, two on the hoses going to the compressor, four 
between the compressor and the manifold which mounts on it, and two on the 
"muffler" (a pressure reservoir present on my model but not present on many 
other 200's, located on the outside front corner of the AC cooling unit in 
front of the radiator).  Most of these will NOT come with any kit you get, so 
you will be hunting for them at parts stores.  Take the old ones and match 
them by eye.

- As noted above, the orifice valve (a small conical screen) is hidden in the 
system.  There is a refrigerant pipe running along the firewall above the 
dryer, and there's one connection right above the dryer.  That's where the 
valve goes.  NONE of the manuals or bulletins will show you this location. 
 My old valve was full of aluminum bits, so I'm very glad I found it and 
changed it.

- The compressor came with dire warnings about keeping the PAG oil in it. 
 Just try!!!!  It mounts upside down under the car, and as soon as I turned 
it into install position the oil started running out.  I drained the oil into 
a measuring cup and made notes on how much was there - because it was 
immediately clear that there was no physical way to keep the oil in the 
compressor during installation.  That's OK - the oil can be added in while 
the system is being charged.  There's no other way to do it, anyhow!

- Even in the moderate warm temps we have now (80 degrees) it takes longer 
for the AC to blow cold air.  I'd estimate time to full cold at about 4-5 

- Given time, the air coming from the vents seems as cold as the original 
R-12. The gents who installed the refrigerant said that they tested the air 
output and it met specs for temperature achieved.

I'm glad that I went for R-135A.  The system seems to be cold enough, the 
cost was MUCH lower than R-12, and even so this job cost more than $800. 
 Here's why:

Remove compressor, flush system:  $200
Compressor, dryer, valve: $363 (Bavarian Parts - NY)
Charge system with refrigerant and 10 oz. oil, including 2 hours labor (I 
left one hose loose at the compressor and cost myself $$): $266

Approximate cost $829.  I won't count the incidental O-rings or the new fan 
belts I put on, which I strongly recommend doing while you're at this.  Most 
of them have to come off anyway to mess with the compressor.

Al Powell
Fort Collins, CO
powellae at
cougfan1 at

More information about the quattro mailing list