Hello,

New to this site and don't know much at all about cars. I have a 2007 Chevy Cobalt. On my way home from work this afternoon, my check engine light came on, the air conditioning was blowing warm air, and the coolant temperature read --- instead of a temperature. Can anyone please help me figure out what the problem may be and how it can be fixed??

Thank you so much!

 

Did you stop at autozone or anything other autoparts store to get the codes read?

 

No I did not. Like I said, I know absolutely nothing about cars. Is that where I should go? Is it safe to drive? I don't want to hurt the car further!

 

Coolant temp sensor possbily is bad.


Reason why no A/C is the computer does not know the coolant temp, and does not want to cause the car to over heat by introducing more hot air over the radiator.

 

Is that why the check engine light is on also?

 

Yes very well could be. Or a broken wire to or from this sensor.

 

go to autozone, delete the code, see if your coolant temp comes back. if it does, you've got a bad ground like i do (mine reads --- all the time and i delete the code and it's fine). it took me 4 coolant temp sensors to realize it was a bad ground instead of sensor. if the --- doesn't change, then you need a sensor. they're like 12 bucks and not too hard to replace.

 

Its the coolant temp sensor... BUT do NOT buy it off autoparts store.... From experience I will tell you to buy one off GM. Did it set cooling fan on high? If so then there u go. Sensor or wiring.

 

yea a gm sensor is the way to go for most of the things on our cars. cheap knock off ones tend to be retarded

 

welp everyone is saying its the sensor. but my issue was actually the T stat, it was stuck open, not allowing the car to get to Operating temp. which would throw the light. and then the coolant telp would blank out ---. and the fan would be on all the time. the A/C will not work as the car "doesnt know" what the temp of the coolant is.

 

what an odd coincidence. My '07 did the very same thing this morning, minus the CEL (so far). Search feature FTW!
Is the sensor hard to replace?
I had noticed recently that the fan seemed to be on a lot, but the car wasn't overheating. So replace thermostat too, just to be safe?

 

you don't need to replace the T Stat unless its bad. maybe others have had an issue with the colant temp sensor. Best thing you could do is to plug in to a decent Code reader adn watch the datastream. see if it is reporting the coolant temp or not

 

Thermostat will go sooner or later buy one and also the temp sensor. Replace sensor and if it does nothing, replace tstat

 

strangely enough, my sensor started working again on the way home. I noticed before i left work that the overflow jug didnt have very much in it at all. Is this relevant? It was only about 65 degrees this morning and traffic was light on the way IN to work, but it was 85 degrees and traffic was heavier on the way home. Do you think that the sensor started working again only because it was warmer and more was in the overflow jug? Coolant temp was 175-ish when it popped back on about 4 minutes into my commute. Got up to 217 in stop and go traffic thru town 20 minutes later. Still no CEL.