I have a 2007 HHR with 135000. I changed the thermostat back in October but my car's coolant gages are flat lining again and the engine light is on. It works sometimes but flat lines again.

 

You put the wrong t-stat in. You need a genuine GM 131-158. The t-stats from the parts stores have a rubber inner gasket that fails, causing the t-stat to stick open, thus the code P0128 and the flat line and the A/C not working.

 

Welcome to the forum.

Download the code from the Check Engine Light system, and post it here (the actual code, and not a verbal description) - and we'll see what advice we can offer.

Also, what brand of thermostat and part number was it that was installed back in October? The one that seems to be the best - ACDelco 131-158 or GM P/N 12622410.

 

7 Coolant Temperature Sensors and 4 thermostats later... Donbrew is correct. Purchase the thermostat he suggested then get ALL of the air out of the system.

I fought that battle for like 4 years. -_-

 

My not sure what brand my dad put in when he changed it. I know he got it from O'Reilly auto parts. My gauges will start working but will stop again. My start on my keyless remote won't work now.

 

Remote start won't work if the check engine light is on... as per design. That's not a new problem.


O'Reilly's probably sold your Dad the cheapest one they had...

 

If he got it from O'Reilly it is not correct. Get it from a GM dealer and specify the partr number.

We all know what doesn't work.

The rubber inner gasket on the t-stat has come off and is holding the valve open. The temp is not rising to 180F fast enough, sometimes it does because the ambient temp is higher.

 

I want to thank you all. Y'all have helped me so much. I now know a little bit about my car. I'm taking it to the dealership in the morning to put it on their machine. My dad wants to know for sure what the problem is. I will past this information to my dad.

 

Well, be prepared to scrape the bottom of your wallet - the dealer will not be cheap. Mine wanted $80 for diagnostics, PLUS another $220 to replace the thermostat. (assuming the code is P0128, since you still did not provide that code)

 

I don't know the code but they said thermostat at the auto parts store. I don't have a problem paying for them to put it on their machine but I'm praying my dad can do the repairs. Thanks for all the help .