1990 Pontiac 6000 heater works great but defrost won't turn on. Switch light works? any thoughts? Thank you.

Asked by Jan 25, 2014 at 09:22 AM about the 1990 Pontiac 6000 4 Dr LE Sedan

Question type: Maintenance & Repair

1990 Pontiac 6000 - Heater works great but won't switch to defrost.  Thank you.

2 Answers


Sounds like a mode door actuator problem. Not sure about your model but older model cars used vacuum to move the doors. You could just have a vacuum line loose. I will do some digging.


Yes it appears to me that yours is vacuum controlled. Look for vacuum leaks. Should be a vacuum hose coming off you intake and going thru fire wall to air controls. There should be a 6 way(line) diverter valve behind the dash that controls which doors open and close. Inspect it for vacuum and vacuum leaks. Hope this helps

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