Was told by PepBoys that A/C is fully charged and holding pressure, and that the compressor is functioning properly -- but air is still blowing warm. They seem to think it's electrical. What to investigate next? Take to dealer or regular mechanic?

If the system is functioning perfectly, then the evaporator is getting cold. If the evaporator is getting cold, the only thing keepingyou from feeling cold air is a hot heater core (i.e. broken heater control valve). Happens on these cars - check it out.

Greg

You may be right! Please see the problem I was having in the Winter:

Intermitten Heat

http://www.brickboard.com/RWD/index.htm?id=756139

Correlated?

I'm wondering how PepBoys determined that the system is fully charged. It seems that the most likely scenario is that the refrigerent level is low, resulting in poor cooling.

Has the system ever been converted from R12 to R134a? If not, then I'd suspect that the refrigerant level is too low. Can you see the center of the compressor turning when the air is on? That is, the area on the front of the compressor inside the pully should turn. If it's not turning, then the compressor is not functioning. It could be because the refrigerant is too low and the pressure cutout switch is preventing the compressor clutch from engaging. If the pressure is OK, there may be an electrical problem with the compressor clutch.

I think the first thing to do is get another opinion. I can't imagine too many circumstances where the charge would be OK and the compressor would be fully functional but there would be no cooling.

Let us know if it's R12 or R134a, and how they ensured that the system is fully charged. That may provide a starting point for diagnosis before you spring for a mechanic's bill.

Robert

Using R12. Now that I look at the bill, Pep did not charge me for the checkup (even though the manager said they checked it, it was full, and "blew cold at times when the mechanic fiddled with the switches or wires (he could not remember which.))

That said, it probably was never checked...

Now here is the interesting part. I called my regular mechanic and he agreed with your assessment that it should not be "where the charge would be OK and the compressor would be fully functional but there would be no cooling." He also asserted that the charge was unchecked.

A few moments ago, I started the car (a 940 by the way) put the air on and left it running for five minutes. The area on the front of the compressor inside the pully did not turn at all during this time. I then turned the ignition off and on again -- and the pully did turn this time. It cycled 10 seconds, stopped, cycled another 10 seconds, stopped, and then cycled for about five minutes but no cold air!

I did notice that one of the two silver pipes that goes into the firewall felt cool to the touch and had some condensation on it...

Thoughts?

You are low on refrigerant.
A side note, Pep Boys, K-Mart, Wal Mart or most of those others similar are not known for having the best help. I had my wife take her 740 to one of them to 'service' it while I was out of town, only to have the guy promptly OVERFILL the system. On my return I put the gauges on and was surprised the compressor wasn't liquid locked. Overcharging can lead to condensor flooding which renders the gas-liquid-gas cycle useless. Causing poor or no cooling, not to mention possibly locking up your compressor.