2006 GMC Sierra - Heater Constantly On


Old 05-03-07, 07:22 AM
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Join Date: Apr 2007
Posts: 2
2006 GMC Sierra - Heater Constantly On


While working on the stereo in my 2006 GMC Sierra I disconnected the heater control module with the 2 knobs to control the heat on the driver and passenger knobs.

After hooking it back up, the heater is constantly on and very hot air (once the truck has heated up) is constantly coming out of the vents, even when the heat / AC is turned off altogether, the fan is turned completely off, and recirculate is turned on.

I called the dealership and told him what had happened and he said "We probably just need to reprogram the heater control, it'll cost about $80".

I hooked up an ODBII scanner and there were no codes and nothing to reset.

It seems crazy that just unplugging it and plugging it back in would break something.

Any suggestions?

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Old 05-03-07, 11:25 AM
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Find the 30amp fuse (green) that is usually labeled "HVAC, Blower, etc". Pull this fuse out for 5-10 mins.

Install fuse and start vehicle. (keep A/C settings OFF)

Let vehicle run for about 5-7 mins.

This should recalibrate the system.

If this does not work, the control panel may be inoperative or the recirc valve maybe inop.
Old 05-03-07, 02:51 PM
Thread Starter
Join Date: Apr 2007
Posts: 2
Thanks for the help.

I followed your instructions, but it is still doing the same thing.

Is the recirc valve where it switches from inside to outside air? If so, I don't think it is that, since I don't have any control over the air temperature. When the system is operating normally you can change the air temperature whether it is set to inside or outside air.

Would disconnecting the battery altogether overnight reset something or help in anyway?


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