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A/C isn't working so it goes to the dealership, they claim to fix it. A day later I can hear a hissing from the vent (video linked) compressor is turning but other than visual I can tell it's operating. Today the wife drives it to work and she calls because the radiator fan is constantly running, I have her hook up the code reader and sure enough 7 faults. One is an ignition coil and the other the thermostat. When I get home I mess with it, engine temp is reading 0 but for the first time there's no hissing in the AC vent and you can tell the compressor is kicking on. I hook up code reader and only the coolant temp is there now, I clear the fault and Temps come back online but the hissing noise is back. I've linked a video, if you could please provide your thoughts I would appreciate your time.
My car does this. Happened last Sunday on a road trip. Drove home with the temp gauge not working, no AC and the fans still running when I would shut it off. I unhooked the battery and everything returned to normal. Took it to the dealer on Tuesday and they said everything is fine. I told them it would happen again. Next time it happens im changing out the temp sensor switch.
That's comforting to hear in an odd way Corvette Mike. This is my first one in my life, and I really avoid buying used (not that I'm rich). Did your issue include the hiss? I debated preemptively replacing it.
No hiss and no check engine light. The temp sensor changeout is very easy. Its on top of the motor by the thermostat. This is fairly comman on c7"s. Mine is a base model BTW.
A/C isn't working so it goes to the dealership, they claim to fix it. A day later I can hear a hissing from the vent (video linked) compressor is turning but other than visual I can tell it's operating. Today the wife drives it to work and she calls because the radiator fan is constantly running, I have her hook up the code reader and sure enough 7 faults. One is an ignition coil and the other the thermostat. When I get home I mess with it, engine temp is reading 0 but for the first time there's no hissing in the AC vent and you can tell the compressor is kicking on. I hook up code reader and only the coolant temp is there now, I clear the fault and Temps come back online but the hissing noise is back. I've linked a video, if you could please provide your thoughts I would appreciate your time.
Diagnostic for P0128 says to check the connector at the temp sensor to make sure the contacts are clean and make contact. A low-temperature display can indicate the sensor contacts need cleaning or maybe the sensor is disconnected (The contacts are susceptible to corrosion). It could also indicate a bad sensor but I think there is a good chance that while somebody was under the hood working on the AC something else may have been bumped.
Bill
Last edited by Bill Dearborn; Mar 25, 2022 at 02:47 PM.
Diagnostic for P0128 says to check the connector at the temp sensor to make sure the contacts are clean and make contact. A low-temperature display can indicate the sensor contacts need cleaning or maybe the sensor is disconnected (The contacts are susceptible to corrosion). It could also indicate a bad sensor but I think there is a good chance that while somebody was under the hood working on the AC something else may have been bumped.
Bill
Thanks Bill, I'll give it a shot. Seems to have been fine sense but I'll check it out to be safe.
Seems so, dealership asked me to bring it in to make sure there's no freon leaks by using t h e UV dye but refigerant did the job. The other fault seems to be fine and everything is running smooth, thanks for asking.
I can't speak to the hissing noise, but the temperature indicator at zero and a screaming radiator fan after shutdown are seeming to be reported more and more. I had it happen in january. Changed the sensor which didn't fix it, so disconnected the battery and that returned everything to normal. I checked the original sensor and the ohm meter indicated it was fine. Two months later and the exact thing happened again. Disconnected the negative and reconnected and all is fine again. No check engine light and I did not scan codes. I'm thinking at this point that its either a battery that is beginning to fail, a lazy thermostat that is mostly stuck open, or both. Both of these occurrences happened on long road trips. Most of my driving is around town 20 minute rides on average.
Suggestion: Carry an Infrared Temp Gun in the car. If/when the problem occurs, pull over and take a reading of the radiator temp and thermostat housing temp. The stock thermostat is around 190+ degrees F. This should tell you if the problem is related to an intermittent thermostat issue.
Also, does the Tach show the colored bars around the perimeter when the issue occurs? This is also an indicator of too low a temperature. Good Luck … hope this helps.
For anyone curious, mechanic ran the UV dye and light with me there. Looks like the AC was drained empty for some reason so he flushed it and add refigerant, ice cold since. The tempature issue never came back, and the rattling was the tensioner pulley. So everyone curious, pop the hood and look toward the bottom of the engine and you'll see the pulley. If it has fluid all around it, it's bad. Now I'm happy with my purchase and she runs perfect. Thanks to those who responded.
Suggestion: Carry an Infrared Temp Gun in the car. If/when the problem occurs, pull over and take a reading of the radiator temp and thermostat housing temp. The stock thermostat is around 190+ degrees F. This should tell you if the problem is related to an intermittent thermostat issue.
Also, does the Tach show the colored bars around the perimeter when the issue occurs? This is also an indicator of too low a temperature. Good Luck … hope this helps.
just saw this, sorry but the issue is resolved and no problems since. Thank you.
This often happens due to failed thermostats. Likely your issue is a sticky tstat. Get it replaced . These don’t seem to last more than a few years specially with track duty: I’ve gone through many and many brands also in my 2 c7s.
the ac thing was likely unrelated or BS from the mechanic as the car turns several things off if the car gets the temperature not at operating range fault. The weirdest part which I don’t understand is why the car changes the temp reading to 0 if the tstat fails. Stupid.
Suggestion: Carry an Infrared Temp Gun in the car. If/when the problem occurs, pull over and take a reading of the radiator temp and thermostat housing temp. The stock thermostat is around 190+ degrees F. This should tell you if the problem is related to an intermittent thermostat issue.
Also, does the Tach show the colored bars around the perimeter when the issue occurs? This is also an indicator of too low a temperature. Good Luck … hope this helps.
The tach shows the colored bars down at 3500 as it appears at cold start.
A/C and Engine Thermostat Issue
