Andre The Giant

When I push in the button for the AC the light on the button goes on and everything is fine for 10 to 15 minutes and all of a sudden the air turns hot out of the vents. I then turn it off for 30 seconds or so and then back on and back to cold air. This is weird. Any ideas. I haven't seen any difference either cruisng along or driving it hard.

WallyP

One possibility is moisture in the refrigerant. This can form ice in the expansion valve and stop cooling. The ice quickly melts when the system is turned off.

Sometimes low refrigerant levels or a faulty anti-freeze sensor will allow the evaporator to operate at below-freezing levels. In humid conditions, ice can form on the evaporator, cutting off air flow - this is not your problem, as you would get no air flow, not warm air flow.

There are other possible causes for your problem, such as a faulty anti-freeze valve that cuts the compressor off too early - that doesn't sound likely.

The small relay in the HVAC control head is a common failure, but I don't see why it would be as repeatable as you describe.

The next time that the problem occurs, leave the system running, pull over at the next safe opportunity, and see if the compressor is running - this will split the possible causes and might make diagnosis easier.

Andre The Giant

Thank you Wally, I will check further next time.

Ricardo Vega II

Andre, look into a faulty heater valve. I just was having same issues on my car today. Found out my valve was not closing and was having a warm AC. Removed hoses that run hot water into heater core and now I have a super cold AC. One of the hoses I looped into engine and the other two I plugged up. I'm set till winter comes.

Here's a great link!
http://members.rennlist.com/pirtle/svc_heatv.html


RVII