A/c Blows Warm Air

[1990ss]

The A/C starts to blow warm air on my 2001 Silverado after it's been sitting and idling after about 10 minutes or so. It's been in the 90's when it's happened but it still shouldn't do that. What would cause this? Would it be the condenser or maybe the drain is clogged up?

[dewfpo]

A clogged evaporator drain won't cause that. I've never seen or heard of a condenser clogging. When the A/C is not cooling, open the hood and see if the compressor clutch is engaged? Once it stops cooling does it eventually cool again on the same trip? What about if you shut the engine off and restart it, does it work o.k. then? Give us more data to work with to try to help you.

 

DEWFPO

[wavery]

Is your radiator fan working?

 

Could be a bad fan clutch. The fan should be roaring when you are idling with the A/C on.

[1990ss]

The a/c will get cold again once I start driving on the same trip. If the fan clutch is bad, will the fan not be turning at all?

[nickvrebel]

Two distinct possibilities:

 

1. is the engine idleling smooth?

if it is stumbling, then the compressor stops then the issue isn't in the a/c - it's the engine. There is a setting in the PCM called "stall saver" that detects when the engine is in danger of stalling out and it cuts the accessories (alternator and a/c) to keep the engine running (or give it the best chance to keep running) as a priority. This will only show as an issue at idle because the engine is unlikely to be in danger of stalling when traveling at speeds that brings the engine over idle speed (and the PCM parameter is rpm based).

 

I've seen this many times, the solution is to:

a. on 1999-2002 throttle by cable trucks clean the throttle body and the Idle Air Control Valve - the IAC is located on the throttle body and is likely clogged or possibly not functioning. This valve varies the air intake when at idle with the throttle closed to maintain a smooth running engine.

b. on a 2003+ throttle by wire clean the throttle body, be sure to get the front and back of the throttle plate. The plate is likely sticking. The throttle by wire trucks do not have a IAC, since the throttle plate is controlled by a servo the PCM commands the throttle plate to move and compensate just as the IAC would have, removing the need for a IAC.

 

2. The fan clutch isn't working. You would hear it if it's the problem, it would sound like an airplane taking off (whirling sound) when you drive around.

[1990ss]

I'll have to check out the fan clutch. It does make alot of noise for a little bit when I take off from a start up. I'm pretty sure it's not the first one you listed. The truck always runs great and idles smooth.