Heat temp shows one thing and digital readout show another


Asked by cincysmodz Jul 08, 2016 at 05:46 AM about the 2007 Chevrolet HHR LS FWD

Question type: Maintenance & Repair

I have a 2007 Chevy HHR LS. My AC stopped working and my temp sensor
show that it is running around 180 degrees but my digital readout in my info on
the dash shows over heating when it idols goes up to 215 degrees? This is a
new motor. I have replaced the thermostat, new head gasket, new radiator and
new sensors. What could be causing this? Any info would help

9 Answers


Return to service shop that installed the new engine and cooling system and have them check it.


I am the service shop! I have pulled the motor twice and went through it all. Take back parts just in case I got a bad one and installed new. Still doing the same thing?


Ok, first why did the AC stop working? NEXT, *is it really running hot..Do you have a hand held temp gauge? Is the electric cooling fan coming ON? if not see if it functions when you turn the AC on.. Did you change the temperature sending sensor / sending unit? Confirm the gauge is accurate* Once again, Step 1.Confirm engine is running hot. Don't use the gauges on the vehicle.. (180 they conflict 215) Then message again! Wow you pulled it the (engine) twice! You had the head checked at a machine shop for cracks? I know you're not the machine shop too!

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I have not figured out why the AC stopped working yet. It is full and the clutch is kicking in. I have read on most forums that the over heating and the AC not working go hand in hand. Do not know if this is true but I have to start somewhere. I do have a fluke hand held. I will let the car run and see what my meter shows. i have replaced all sensors twice just to insure I did not get a bad one. I did have the head done and had it checked twice because I was unsure of it being done correct the first time. Not that I did not trust the shop just wanted to eliminate it as a problem. Let me run this thing and see what it shows. Thanks!!!!


Ok, Here we go. I used my inferred thermometer and the block and head only get around 190 degrees and the readout shows 215 and the Gage shows 180 and never moves unless you unplug the temp sensor and it goes flat. The AC was an over fill problem that we think we fixed yesterday. So the only problem I am getting now is the readout saying it is over heating. Hooked it up to a handheld OBD II and it shows the same temp and the readout. So while I was letting it run to get hot I had a engine light come on. The code was P0420.... Catalyst System Efficiency Below Threshold (Bank 1) So I guess I need to start with replacing the 02's or just get a new converter because that might be the over heating problems?

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Good work! connect a vacuum gauge to read direct intake vacuum see if the cat is causing back pressure I expect approx 17-21Hgin of vacuum Ok... The upstream HEGO as you know is one of the only "active" signals to the PCM (computer) that controls the fuel ratio / fuel trim 14.7 is the goal... If its slow to respond due to mileage or age, or a bad catalytic converter it can cause the mixture to be lean (creating more heat) The downstream 02 sensor merely reads the difference in exhaust gases after the converter its NOT controlling anything. I changes HEGO's / 02 sensor after 80,000 miles it pay rewards.. fuel economy...mileage, and engine response.. Please keep me informed on The...YOUR progress! regards


I have yet to check the vacuum on the intake. I was driving to work and the temp gauge just flat lined. The readout on the dash is ----- I have a new temp sensor on its way. When the sensor flat lined the AC stopped working again. I will post results as soon as I have some.


Put in a new Temp sensor and it fixed the problem.....For a few hours. The temp sensor fixed the problem. The temp showed correct on the dash and in the info center. My AC started working correctly as well. Drove to work and everything was fine. It takes me about an hour and 20 mins to drive. No problems with the AC. Well got in the car to drive home and with in 20 mins the gauge drops to nothing and the info center shows -----F and the AC stopped working. Pulled codes when I got home and it was P0128 (A P0128 is a code is an indication of a faulty thermostat or ECT (engine coolant temp sensor). The manufacture designs the engine to run at a specific operating temperature for the most efficient operation. The thermostat regulates the coolant between the engine and radiator.) I have put two (YES) two thermostats in this car just to insure I did not get a bad one. Now after resetting the code the gauge is working and info center is correct and my AC is working again. HELP ME!!!!


Get a thermastat without the rubber seal in center and your problem will go away. T he rubber seal in center of thermastat comes off holding thermastat open and it takes too long for engine to get operating temp. it needs to reach this temp. in a certain amount of time, mine did it 4 times untill I got one without center seal and no more problem.

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