my fan is always on and my coolant temp is blank and my a/c wont turn on cause of this.

Asked by May 18, 2013 at 08:03 PM about the 2008 Chevrolet Cobalt

Question type: Maintenance & Repair

13 Answers


you are not alone--- have 07 4-door for last 3 years- in last six months the coolant temp dashes out (---) and the a/c wont come on- some times i get numbers back and the a/c works until the display dashes out again-this also kicks on the check engine light- had the trouble code checked and was told it was coolant temp below norm- changed the engine coolant temp sensor ($25. & 2hrs my labor) worked great for 3 days and then display dashed out again and has stayed that way-checked haynes manual wiring diagrams- both the a/c and the temp sensor feed into the engine control module- checking this means taking it to chev auth service center which means lots of cash- my next step is to change the thermostat ($8.) THIS IS THE MOST STUPID THING I HAVE EVER HEARD-WHY WOULD THE ENGINE COOLANT TEMP KEEP THE A/C FROM WORKING- THANKS CHEVY- sorry i don't have the answere yet- if you get one that works please post it - i will do the same-- good luck

11 of 11 people found this helpful.

im having same problem with my '09 cobalt now. has anyone figured out the resolution??

6 of 6 people found this helpful.

Having the same problem with my old lady's parents car

3 of 3 people found this helpful.

I have the same problem! 2007 4dr sedan! I have changed the Egine Coolant Temp. sensor twice and still about three days and then it goes out again. Still dont understand y the A/C goes out? Any luck anybody please let us know....

3 of 3 people found this helpful.

I had the same problem too, it turns out the thermostat needed to be replaced.

1 of 1 people found this helpful.

I have a 07 Pontiac G5 GT, I was on the highway with roadwork traffic going really slow. When I looked down and noticed my temperature gauge was blank and or reading this ( --- ) and because we were not moving as fast and the noise was down I heard the fan running. I have a 30 minute drive home from work and it remained on the entire way home. I'm thinking it's either the thurmoustat or the temp gauge sensor. But it hasn't thrown a code or check engine light this could also be due to the fact that my internal computer is absolute ass and it's not working properly either.... So I'm at a loss. I guess I'll drive it until it breaks down in my case the fuel lines are already leaking and I purchased the car used about 4 months ago.... I definitely got a lemon on this one.... But if it isn't one of the two things I said of previously then I might just strap a pound of c4 to the damn thing and watch it go!!!

1 of 1 people found this helpful.

My car is having same problem. I change the temp sensor and nothing has change. I change the thermastat about two months ago. Any answer will help thanks.

I have same the exact same problem in my 2007 cobalt. I changed the temp sensor. Worked fine for a few days and temp went dashes A/C stopped working. Cooling fan runs from start-up. If I unhook my battery for a few minutes, then everything works fine untill my temp reaches between 145°-170° then it Blanks out on the dash, the cooling fan comes on and the A/C stops working. I unhook the battery and it's like groundhog day..I think they need a recall. I'm sure you do too..But that said. If it's below 40° ambeiant temperature outside, It works fine. The fan comes on at 210° the AC works fine. But the engine temperature will drop down to 156° and fluctuate between there and 169°.. If it's 50° outside though​, it will stop working when the engine temp reaches around 150°. Help a fellow bro out please. Do I need a new A/C / Heater controller that goes in the dash. Is it a high low fan sensor. Is it the technology made by aliens, and humans don't have the brainpower to figure it out...Or it's a good little money maker for dealerships, bingo! Yeah I know. Trade secrets and all...


This is definitely the thermostat. Two screws easy fix. On my thermostat is have a seal in it. And I just change mine a month ago I was like there is no way. And yes it went bad. Theses cars are well known for this. Change yours. Put a bucket under the car. Because antifreeze will go everywhere. Change it. And tighten up then add. Antifreeze drive up road until thermostat opens and will fix the problem. I'm a girl. If I can fix it. Anyone can. Good luck.

1 of 1 people found this helpful.

I have the same issue, ECTS waa replaced along with the thermostat, just had the collectors and pigtails replaced and it lasted 3 days only to stop reading a temp again

I changed the thermostat, worked fine for about ten miles and done the same blasted crap again. I'm at a loss now?

My next step is to Chang the coolant. Perhaps someone has added regular tap water to the system. This could cause a low voltage short as it travels thru the cooling system. Only deionized water ( has all minerals removed that can carry a current) is to be used. Will be a few days before I can try this. But I will post an update when I find out if this works.

I don't have an answer yet either. I changed my thermostat and it worked for about 4 days. When I took the old "fail safe" thermostat out, it was fine and not stuck open like it would have been had it failed. A week later I changed the sensor. It worked fine for a day and a half. Cleaned the connections on the ECM and it worked fine for another day. It's all back to the same dashes, engine light on, no a/c. I'm out of ideas, patience, and money.

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