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Jared D
Jared D, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1452
Experience:  Shop Supervisor at County Fleet
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I have a 2011 Tahoe Lt with manual HVAC. What would make the

Customer Question

I have a 2011 Tahoe Lt with manual HVAC. What would make the front and rear A/C come on after the car has been shut down for 10 min. or more? The A/C is shut off before the car is shut down, no key in the ignition switch, car parked and all the doors and windows closed. Of course this is an intermittent problem. I have parked the car everything off and then happen to come back out the garage only the hear both front and rear A/C fans running on high. I have also parked the car in a parking lot only to come back out and find them running. I have to put the key back in and turn the ignition switch on and then off so that they will shut down. If I don't happen to hear them running they will run until the battery is low. This is not an afterblow function that is only on automatic HVAC systems.
Submitted: 9 months ago.
Category: Chevy
Expert:  Jared D replied 9 months ago.

I had a very similar concern on a GMC sierra. The ac blower would either stay on after the truck was turned off or the blower would turn on while the truck was sitting in the parking lot and run for who knows how long.

Do you plan to fix this yourself?

If it's the same concern as the sierra I had then it's a fairly easy fix.

Customer: replied 9 months ago.
I plan to fix it myself. I have all 5 volumes of the GM 2011 service manual
Customer: replied 9 months ago.
What is the Fix?
Expert:  Jared D replied 9 months ago.

Sorry, got pulled away for a sec there.

You'll want to replace the blower motor resistor. In the 2011 model GM calls it the blower control module.

Here is the method for replacing it:

Expert:  Jared D replied 9 months ago.

What is probably happening is the module is shorting internally and causing the blower to be powered even though there is no signal from the HVAC control head.

Customer: replied 9 months ago.
does that power the rear AC also?
Expert:  Jared D replied 9 months ago.

Sometimes the rear AC unit has it's own module, let me check the schematic.

Customer: replied 9 months ago.
I just looked at the schematic it shows one for the auxiliary blower also. I guess I will change both front and rear.
Customer: replied 9 months ago.
Thanks ill give it a try
Expert:  Jared D replied 9 months ago.

Is the rear blower coming on also? I can't find a schematic from GM that separates them out.

Expert:  Jared D replied 9 months ago.

There is a separate resistor for the back unit, but it doesn't indicate the wiring path in the repair manuals.

Customer: replied 9 months ago.
the schematic for the rear is on page 10-229
Customer: replied 9 months ago.
sometimes just the front, sometimes just the rear and today both were on
Expert:  Jared D replied 9 months ago.

If both are coming on I would suspect a short in the control head. Do you have a scan tool to look for trouble codes in the HVAC head?

Customer: replied 9 months ago.
no my scanner wont read HVAC I may have to take it to a shop
Expert:  Jared D replied 9 months ago.

I think your best bet will be to look for codes, then if nothing comes up replace the resistor in the front unit and see if it stops acting up. If it does, and the rear continues to come on by it self then replace it as well. It could be a strange coincidence that both resistors went out at the same time.

Expert:  Jared D replied 9 months ago.

Good morning,

I wanted to check and see if you needed any additional help.

If you no longer need help, please don't forget to rate.

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