[legendary70]

Hello all.

OK. 2017. I have been having to undo the negative terminal on the battery to fix this. My AC will not work at times, usually when i turn the car off i can hear the fan running non stop. that means the ac wont work when that happens. AFter i do the negative terminal all is fine. but it has been happening more frequently. what can it be? thx

[Drags1998]

Coolant temp Sensor? Low coolant?

[FlukeSS]

Originally Posted by legendary70

Hello all.

OK. 2017. I have been having to undo the negative terminal on the battery to fix this. My AC will not work at times, usually when i turn the car off i can hear the fan running non stop. that means the ac wont work when that happens. AFter i do the negative terminal all is fine. but it has been happening more frequently. what can it be? thx

How long have you had the car?

I've heard about this problem related to electrical on my 2007 Impala SS, but the cause in my case is unusual

Does your car have a sunroof? IF not forget what I said.

In my case the drain railings by the sunroof were blocked and caused water leaking into the car which shorted out the Vent switch of sorts.

Very odd issue.

[ctrlz]

Originally Posted by Drags1998

Coolant temp Sensor?

Check this on the dash readout.

I would search the old threads, as there are several reports of the "fan keeps running" variety.
Not sure what ended up being the most common cause.

[lt4camaro]

Water temp not getting up to at least 180 degrees and or taking way to long to heat up to that temp.

[legendary70]

Originally Posted by lt4camaro

Water temp not getting up to at least 180 degrees and or taking way to long to heat up to that temp.

So it might be the themostat?

[ctrlz]

Originally Posted by legendary70

So it might be the thermostat?

yes, sounds that way.
But you should see evidence of what your thermostat is doing on the temp gauge. If it is sticking open you will see it.

[Yang N’ Bang]

I’ve had this issue in the last few months, specifically when the car starts in 30-50 degree weather in the morning. Temp gauge would be bottomed out not moving, a quick run with the code reader and a quick clear would set the car back to normal, temo was fine and all, no issue, replaced the temp sensor, still happened, replaced the T-stat, still happened. I came to the conclusion that the thermostat just doesnt open fast enough in the cold weather so the sensor panics and throws the fans on full blast. Note I live in AZ so I never really run my heater, but ever since I’ve kept my car at about 85 degrees to get the heater rolling, have not had the issue since.

[S.Macias]

Mine did the same thing. The fan wouldn't turn off even though the car was off. Did it probably once a month. After the second time I took it in and have the thermostat replaced. Cost about $450. No longer does it.

[legendary70]

Originally Posted by ctrlz

yes, sounds that way.
But you should see evidence of what your thermostat is doing on the temp gauge. If it is sticking open you will see it.

I forgot to mention. When it does this, the temp gauge does not move even after driving for a while?

[legendary70]

Originally Posted by S.Macias

Mine did the same thing. The fan wouldn't turn off even though the car was off. Did it probably once a month. After the second time I took it in and have the thermostat replaced. Cost about $450. No longer does it.

Just an FYI. When mine does this the AC dont work....heater does. Take the negarive terminal off and everything back to normal.

[lt4camaro]

Originally Posted by legendary70

So it might be the themostat?

Yes, did you ever swap out the original for a aftermarket cooler thermostat or did someone else? Some of those stats Orings or rubber seals are known to split and slow down warm up. Or the original GM stat is partially open and again slowing down the getting up to temp process or not getting hot enough period, especially during the cold weather.

[arpad_m]

My guess is also the coolant temp sensor or the thermostat (less likely, because a battery disconnect wouldn't fix a stuck thermostat). Just had to get both replaced on wifey's truck

OP, if you have an OBD-II reader, you can read off the codes and hopefully get a clear idea what exactly it is before firing the parts cannon at it.

[ctrlz]

Originally Posted by arpad_m

My guess is also the coolant temp sensor or the thermostat (less likely, because a battery disconnect wouldn't fix a stuck thermostat).

Agree. Chicken or the egg scenario.
Temp sensor is cheaper and easier to get to than thermostat.


Load up the oil temp reading on the DIC. That should follow the coolant temp although slower to warm up. If that warms normally I would suspect the sensor over the thermostat.


The other thing to do is feel the radiator return hose to see how warm it is. That's old school and I'm not even sure how easy it is to get to on our car.