G3GM 1973 to 1977 A-bodys. Chevelles, Monte Carlos, El Caminos, Laguna, 442, Cutlass, Malibu, GTO, LeMans, Century, Regal, Grand Am, Grand Prix, Sprint, Gran Sport, Can Am, Hurst-olds, and other 73-77 A-bodies
Not a GM a body but should be the same system I think. Its on my 76 GMC motorhome. Im trying to convert to r134a. Ive flushed the whole system new dryer and o rings. Problem is I cant get the vent temps under 70 degrees... On my 70 chevelle I adjusted the POA valve and got it to 38 degrees out the vents. The motor home doesnt have a POA it just has an expansion valve. Any ideas here? I can get the pressures really good (around 22-25 on the low and 300 on the high 90* outside). Im gonna try changing the Expansion valve and see what happens. I didnt know if there was a newer expansion valve either that works better with r134a.
It's a pretty simple system and it sounds like you have good pressure readings, so that should rule out compressor and amount of refrigerant. So I'd suspect the expansion valve too. Do you have access to the a/c core in the evaporator? If so, can you check to see if the thing actually gets cold?