Hey everyone,

This is my first post but I have checked in from time to time. I have a 2007 HHR about 181.500 miles or so. It's been having some weird electronic glitches that I can live with such as the seat belt indicator light coming on even though it's buckled (and I'm the only one in the car) and the remote keyless entry has worked funky since I got it last July/August.

New issue though that looks like it may be a thermostat?

Just noticed tonight that my temperature gauge was pretty much on 0 despite running for about half an hour on a drive and the reading on on the DIC is ---F. Heat works okay and I guess the air does as well. Noticed when I shut the car off it still sounds like the fan is running (cooling fans?)

Most things I've looked at seems to go back to thermostat. Is that the likely culprit?

 

Yes change the termostat. Use the Delco one only #131-158.
Change coolant at the same time with Dex Cool antifreeze
Drain out what you can and add the 50/50 mix that is bought in the one gallon container.

 

Welcome to the site, and burp the coolant system

https://www.chevyhhr.net/forums/how-...l-p0128-24493/

https://www.chevyhhr.net/forums/how-...-system-60614/

 

Thank you for the replies. Will likely try to get it fixed one way or another tomorrow or at least this week. Oddly, the reading came back on it after posting this with the exception of a moment today where it flat lined but then came back after parking and running into Walmart and then restarting it to go home. A lot of times it does seem to run a bit cooler than normal and at other times it fluctuates up and down a lot. Not hot at least from the gauge and temperature reading but it might drop from 170 or 180 something to just over 160 in a second or less. Especially at idle or when starting from idle or a stop. So it seems like at times it works or tries to but clearly not right.

 

When the t-stat gets stuck open the engine does not warm up quick enough so a P0128 happens and the temp reading flatlines and you hven't mentioned it but the trans will shift hard.

 

I've had the P0128 without the trans shifting hard because of it.... Just flatline display, no reading on the analog display.

 

My 2.2 the remote start wouldn’t engage with the P0128 and the AC won’t work either.

 

Hmm, yeah I can't say I have specifically noticed that. There is no CEL on the dash and it's been driving okay. It's had an exhaust leak so it's noisy. But I haven't really noticed slipping/hard shifts. Which should be noticeable. Previously had a Cavalier and one of the guys at Walmart managed to unplug the speed sensor which not only lead to flat line on the speedometer but significant clunking and hard start from a stop sign or something until it eventually went into limp mode.

 

That is a possible symptom, not definite, the temperature gauge is indicative of a stuck open thermostat, don’t go for the cheap MotoRad or Stant units , get the AC Delco 131-158 thermostat.
As mentioned prior.

 

Other cause could be bad sensor or sensor wires. But still should have some sort of code from your description.