I have a 96 S-10 2.2L that the A/C blows cold while it's idling but when I start driving the air gets warm. Compressor still runs, just blows warm. Once I come to a stop light it gets cold again. Any ideas what can cause this? Thanks in advance.

 

I am not familiar with this truck but here is a idea if the temp blend door is vacuum operated; maybe the loss of vacuum at cruising speeds is causing the temp blend door to move.


test this theory by reving the engine to 2500rpm, transmission in park, for 50 seconds and see if the a/c goes warm

 

At higher RPM it does cut out, less air flow from the vents as well.

 

there must be a vacuum leak or a bad check valve in the vacuum controls for the blend doors. maybe someone familiar with this hvac system will chime in.