I have a 2009 HHR. I have brought it into the mechanic and he has check all the typical refridgant and compressor issues. What happens is the air conditioning works great until the outside temperatures reachs 90 degrees plus. Then the engine temperature gauge stays at zero and the air conditioning does not work. The temperature guage and the AC work fine unless the temperature is very high outside. Any ideas? My mechanic is stumped. Thanks in advance for your help!

 

Yes.
98% chance your engine thermostat is bad. It will cause the computer to register a fault, makes the temp gauge show - - - and the computer then shuts down the AC compressor. Have your mechanic pull the codes. If there is one, it should be a P0128. That code almost always points to a bad thermostat .
If you have it replaced, only use a genuine AC Delco thermostat. Some of the other brands don't always work correctly.

 

Welcome to the site, X2 as FMG has pointed out , ensure you get an AC Delco 131-158 180 degree thermostat.
And make sure to have the coolant replaced with 50/50 mix of Dexcool and water.

 

This is the most awesome resource you guys are brillant and generous. A bad engine therostat is what I thought too when I figured out the connection. My mechanic said maybe a "wiring issue" which didn't make sense to me. I will follow your advice and report back.

 

We shall wait !
It amazes me how these guys come up with these ideas.

 

He's a really good and fair mechanic but you can't know everything and he didn't charge me a penny for looking at it... so you know he was just speaking off the cuff when I told him my discovery.

 

I agree, give him our site , we can help out with his other HHR customers.