2004 MCS w/ auto air. 109K. Recently my air conditioning seemed to be running warm. Engine fan new and running fine. Cabin air filter new. My mechanic evacuated and recharged the R134 and found no problem. Compressor engages as it should. I suspect that something is allowing hot coolant to continue to circulate through the under-dash air handler at a time when it should not, thus 'competing' with cooled air; either that, or some servo is failing to close off heated air into the passenger compartment. Does this problem sound familiar to anyone? Solution? TIA.

 

bump

 

So does the A/C blow as cold as it should for the first few minutes, before the engine coolant has had a chance to heat up? The coolant thermostat should be keeping the coolant recirculating through the engine (and not through the heater core under the dash) until the coolant is at least up to 190 °F or so.

If you're not getting ice-cold air during the first few minutes of operation, then there's probably something else amiss.

 

Good point, but no, even when the engine coolant is cold, the a/c is not up to its usual cooling.

 

sounds like it could be an orface/expansion valve issue if the pressures are OK.....
Manual or auto AC?
Like said above the AC should be COLD long before the motor can make any real heat....

 

auto ac

 

I have a similar issue. My AC only blows cold while underway. When going slow or stopped it heats up. The shop I took it to replaced the expansion valve hoping to fix the problem. They told me it has pressure but only about half of normal. Do I need a new compressor?