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Climate Control Slow to Begin

whitesierra-ride

By whitesierra-ride
in Ask A GM Technician

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whitesierra-ride New Member

whitesierra-ride

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2008 Sierra auto climate control is slow to kick in. The control will be fine then I stop for 20 minutes and get back in, it's very cold outside and temperature gauge will register but is not vertical. The auto climate is on and heat set to 71, but it takes 5 - 10 minutes before the fan kicks on high to blow heat. Sometimes it works fine, most times it takes a while. I tried turning the ignition on and off, tried using manual heat, nothing helps. What's up?

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Auto climate control will wait until the coolant temp is high enough to heat the air quickly. The lower the outside temp, the longer it takes to get warm enough to signal the system to run fan on high speed.

You may want to check to see if thermostat is working correctly, as well as the ambient temp sensor. You may also want to find out what the temp is according to the ECM.

 

I had a 2000 GTP that would not set the fan to high, or even shift trans into lockup in high gear until I had gone more than 5 miles on any cold winter day. I did not warm car up, still don't.

whitesierra-ride New Member

whitesierra-ride

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Maybe the ambient temp sensor, it has a noisy fan. However, lately there is a buzzy noise, like a relay trying to activate, coming from the passenger side somewhere. It buzzes 2 -3 times then the fan cranks and heat comes out. I think this may be the HVAC blower motor resistor or relay and I think that is under the passenger dash area.

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