I have a 2008 HHR LT that has some intermittent problems. The temperature gauge sometimes stops working and that causes the A/C to fail also. Possible related, sometimes the driver info center doesn't display and the radio lights are out but the radio plays fine.
I've had the temp sensor and the thermostat replaced. Two shops have checked the wiring and found no problem. It acts as if there is a bad ground as sometimes the radio lights and driver display are faintly visible but not bright.
TB 08-08-49-017B offers a similar problem for the temp sensor and suggests reprogramming the IPC.

Any other opinions?

 

You need to replace the thermostat, I had mine replaced several months there is a whole forum on this, I bought mine from O'Reileys, good luck.

 

What is a IPC?

 

You do know that the dash lights will change on their own when the ambient light changes, right? So, may be no correlation.

 

Already did......

 

I wonder if the OP has some of the old thermostat rubber hung up in his new thermostat? The light's on the radio, DIC going dim sounds like normal operation when the auto headlights turn on and dim the display.

 

Good point on the rubber from the thermostat - someone here recently reported the same. Sounds like it's time to remove the thermostat, and inspect it, and probably follow it with a good flushing of the system (without the thermostat in place most likely).

 

IPC is your Instrument Panel Cluster