I just finished some work on my AC - evac and recharged with R12, replaced drier and just got the aux fan replaced and running. AC still does not cool as well as I had hoped. I guess that's my first question - what are realistic expectations for my Oklahoma heat? Today, it's 90+ and I'm lucky if I get vent temps down in the 50's (on my '72 250, which I converted to r134a, I get vent temps in the low 40's). If the car sits and idles, it is really bad as temps raise in to the 70's. I think I should be getting more than a 30 degree drop between ambient and vent temp???

If I should be getting cooler air, where should I look? FWIW, this car has the ACC, version 2 system. I have checked the heater hoses to see if I am running coolant through the heater core all the time, but I think the monovalve is working properly. I did not replace the expansion valve - would that cause some of my problems?

Thanks for any help - due to this board and all of the good suggestions, i have made loads of progress with this car.

Ryan

1978 300D

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

Yes, it may be stuck and won't open fully to allow enough liquid refrigerant to the evaporator hence minimal cooling. When changing the dryer you could have introduced contaminants that lodged in the expansion valve or contaminants (e.g., metal particles from the compressor) could have already been in the sytem. Whenever I've opened an A/C system, I've always replaced the expansion valve along with the receiver/dryer. Also, how long did you pull a vacuum? Many say you should hold it an hour or more to pull all air from the system. Lastly, the differential between duct temperature and ambient depends alot on the humidity. IIRC, with low humidity (30% or so) you should see a 40 plus degree F difference. With high humidity (80% plus) it is significantly lower maybe only 20 to 25 degrees F, IIRC.