Hey everyone!
I have a 2008 HHR LT 2.2L My temp gauge has flat lined on me causing the AC to stop working as well.
I've read discussions in this problem already, and I have changed the thermostat (twice) and the temperature sensor. I still have the same problem.
Does anyone have any advice on where to go from here?
Any help would be greatly appreciated!

 

Hi David to the forums!!

Did you use the proper ACDelco 131-158 thermostat? Other thermostats tend to cause problems, especially aftermarket. GM part number 12622410

 

I did, twice. Thinking maybe it was a bad thermostat, but still, the same problem.

 

The temp sensor or it's wiring.

 

Next step would probably be to check the wiring for the sensor. Hopefully donbrew can help with that procedure.

 

Visual inspection is all I can lend.

 

Burp the cooling system.
To do so, park your HHR front end higher then the back, or simply jack up the passenger side front, run the engine to temp ,?let cool, remove the rad hose cap and top it up.

 

Or take it to a trusted cooling system tech and have them pull a vacuum on the cooling system, after you verify the functioning or failure of the Temp Sensor

HHRs are notoriously difficult to "burp" after opening the cooling systems up, the highest point is the heater core, so if the "nose high" method still leaves air entrained in the system. Having it put under a vacuum will evacuate the trapped air.