Need help with cabin heat and AC blower fan.

[mymtnhauler]

Wile coming home from Christmas shopping late last night. We noticed that the blower fan would only work on the high setting. #@$%! What would cause this and how do I fix it? Thanks! OOOPS my bad, my truck is an 05 3500 SLT sport.

 

[B.G. Smith]

The speeds of the blower motor are controlled by a resistor block, it is located on the AC housing, usually under the glove box. bg

 

[DNDracing]

Second BG's resistor block suggestion. Voltage to the motor is run through the resistor and reduced to get the motor to run at the lower speeds. If you only have high, the resistor has most likely failed. It is under the glove box. Not a bad fix, a wire harness connector, and a couple screws. Part was about $50 if I remember right. The one I got had a "limited lifetime warranty".

Hardest part is getting at it under the dash.

 

[justme]

DNDracing,

Where did you get a "limited lifetime warranty" part?

 

[DNDracing]

Bought it at a local Detroit area auto parts store called Murray's, which was bought by O'rielly's, not sure if they have them still.