Temp gauge flat lined changed Therm already
 

So, I have been lurking on here since I bought my HHR three weeks ago ran into the thermostat issue one week in after looking at post here with the flat line and --- coolant reading. So driving today and it flat lined again and knowing that I put a brand new one in two weeks ago, I was wondering if anyone ran into anything else that can cause it?

OK, whose thermostat did you use. If any besides the dealer, some people have been having problems with the thermostats purchased at the corner store.

Welcome stalker.

Autozone

Details about your ride would be nice.

Year, Model, Any CODES that may be stored...

Yeah, the GM one apparently doesn't have that rubber gasket around the valve.

And sometimes the debris from the previously deteriorated gasket gets caught in the valve of the new thermostat and jams it open as well.

Or it might be the temperature sensor - the way to tell is to use the digital display and watch the temp as it warms up - if it blanks out while kinda stuck at 84F or so consistently, I'd suspect the thermostat. If it blanks out well before that on a regular basis, then I'd suspect the sensor.

2007, LT no codes

From what I remember from all of the other threads on the subject:
The temp sensor could be bad, the t-stat could be bad, the coolant could be low, the fuse box could be loose, the PCM connector could be faulty, a wire could be shorting.

When it flatlines will the A/C operate? Does the Check Engine Light illuminate? Any other symptoms?

Okay so I didn't have any codes thrown the first time it flat lined, didn't notice that it did the AC stop working and first thought temp gauge and it was flat. Checked here changed thermostat which was bad. No problems till earlier tonight, air stop working again and gauge was flat once again no codes thrown, just wondering if anyone else had something else going on before i go out in the morning and take the housing apart and check the thermostat.

Check coolant level first and burp any air.

Yes, lots of other people have had the experience, or nobody would have responded to your thread. Sorry.


Oh, I just remembered another thing: DexCool tends to get gravelly with age and heat, this gravel collects in the bottom of the recovery tank, when enough gets down there it clogs the outlet so that the normal "give & take" of coolant cannot take place. That causes several problems.