I have been having some problems with my A/C on my 94 with the system seeming less cold the longer I drive. I checked the pressure and got about 32 on the low side and 250-260 on the high side with the A/C set to 60 degrees and about 75 degrees outside. The low side pressure is a little low, but the high side seems really high. I thought I read something about that on the forum before, but I can't find it now. Any help would be appreciated.

 

Both seem high - but you need to take pressures with both fans cranking and the engine at 1200 to 1500 rpms. Make sure the windows or doors are open and stick a digital thermometer (a 5 buck one from the grocery store works fine) in the center vent. Also, get the front end away from anything that will block airflow - like a garage wall. R134 - at 32 psi - is 37 degrees, but with with 5 to 8 degrees of superheat, the Evaporator is in the 40's and it's giving up a few more to the ductwork, so it's probably above 50 at the vent. It should be better than that if it's 75 at the Condensor.

On the high side, 2.2 to 2.5 times the Condensor air temp is a good guideline, but R134 will eclipse this when it's 85 or better so make sure it's got decent airflow - bottom feeders like the Vette can easily be 10 degrees warmer at idle. I don't know where the outside air temp sensor is on the '94, but if it's buried on the Radiator Shroud (like on my '89), see what it's showing on the Display.

If pressures remain elevated, I'd guess the orifice has some junk in it which wouldn't be unusal after 15 years. Make sure the Nippo hasn't given up it's shaft seal - look for oil on the hood above the compressor. It isn't difficult to start over - you'll need to score a vacuum pump, orifice, seals and a new dryer; plus some oil (3 or 4 ozs for the dryer) and a couple of cans of R134. Shouldn't be more than a $100.