Question about 1990 GMC Sierra

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Heater works defroster does not

The heater works just fine but when i turn on the defroster the heater still stays on.i am not sure if it is the ducts or the controls.

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  • clalexy Jan 11, 2009

    I have the same problem. The heater blows great but when I move the lever to defrost the heat to the floor slows down and the defrost baerly bolws. It is something to do with the control doors in the heater duct. 1990 GMC Pick Up.

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  • 176 Answers

It sounds as though you're having problems with your controls...if it were the ducts...you'd get some kind of a air current..even a faint one

hope this helps

Posted on Jan 03, 2009

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