HHR a/c quit working and temp gauge doesn't work
 

I have a 2008 HHR and the A/C quit working yesterday and I noticed that the temp gauge also is not working. I've checked all the related fuses and they are ok. Any ideas as to what it might have happened?

Most likely cause is the thermostat is jammed open (due to a deteriorated gasket on the internal valve) - this makes the engine slow to warm up as the thermostat can't close when it cools down.

The computer detects that it did not warm up fast enough so shuts off the temp gauges, and as a byproduct kills the A/C. The Check engine light will SOMETIMES light up depending on specific parameters - and will create a P0128 code. The condition will occur more frequently as the overnight temps drop as the engine will take longer and longer to warm up.

Check out this how-to - https://www.chevyhhr.net/forums/how-tutorial-library-21/how-save-$350-00-thermostat-replacement-2-4l-p0128-24493/

Thanks for the help. I have a 2.2 and it doesn't seem to look like the picture in the repair. I called Chevy and was going to have them diagnose the problem and on the way to the dealer the temp gauge started working and so did the A/C. No sense in taking it to the dealer if the problem doesn't exist. I'll see what happens.

No, the problem is not gone - it is just waiting for the right conditions again. If it isn't something you can handle by yourself - just take it to the dealer, but you likely will have to wait until the CEL lights up (meaning it has created a OBDII code) - and be prepared to lay out some big $'s as per that link above.

The problem will come and go, depending on how long it takes the engine to warm up. IE: if it happens first thing in the morning, drive a bit, shut it off for a bit, and when you restart it, the problem will not appear (cause the motor took only a short while to warm up). It shouldn't cause much of a problem other than the A/C not working and you being unable to monitor the engine temp - but it should not be left too long.

Other possibility is the temp sensor.