AZ Roadrunner

My service shop has been unable to determine why my 2004 C5's AC refuses to come on while the car is idling and parked once the outside ambient air temperature is above 100F in the hot Arizona summer. The system freon level and pressures were gauged and all is fine. What happens is, no matter how low you set the climate control to, the light just flashes. Once you get going down the road, the AC starts working normally again. The radiator cooling fan(s) were also checked out and work correctly. Appreciate any ideas for my shop techs before I take it to the local Chevy dealer for a likely rape ($$) job.

dadaroo

Seems like something could be funky with the head unit. I don't think it would be the outside temp gauge. Are you reading the outside temp at 100F+ using the head unit?

I bought a spare head unit and have used it for testing friends cars to help shorten diagnostics when things are "strange".

Not at home to help with any further input. Before I took it to a dealer who is going to redo everything you have done so far I would consider getting another unit to try. One should not cost more than what the dealer is going to charge for the first 1 1/2 hours of diagnostics.

If you need a link on removal I have that at home also.

I assume you have pulled the onboard DIC trouble codes to see if they show anything. If not you need to do that just to see if anything shows up before you go further. If you don't know how I can provide the info on doing that.