All,

I have a 2009 Tahoe and the rear HVAC fan only runs on low speed. It is an LS model. I have tried changing the module/resistor in the duct near the fan and it made no difference. Have not seen this problem discussed and I don't really know any trouble shooting I can do. Was thinking maybe replace the control switches, fan speed temperature, and vent but that is a guess also. Any help will be appreciated.

Thanks!

 

Probably the auxiliary resistor is on the fritz.

 

That is the part I changed, it did not change anything.

 

then your high speed relay might be fried. Check a wiring diagram.

 

Update.

Turns out the AC is stuck in mimic mode. Changing the front fan speed will change the rear. Also vent locations are controlled by the front.

Any ideas on what could cause this?

THanks.

 

the driver holds the master control

 

Yes. The driver controls change the fan speed and vent location. It is supposed to revert to back seat control as soon as the back seat controls are moved but it does not.

 

Does anyone know if this could be the rear controls on the ceiling? I don't have any adio controls, just HVAC.