1997 GMC Safari heater control unit

Tiny
JEB STUART
  • MEMBER
  • 1997 GMC SAFARI
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 235,000 MILES
Selector switch for changing from floor to dash to defrost doesn't work. Is there any common reason for this condition?
Saturday, June 6th, 2009 AT 2:57 PM

1 Reply

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Hello, if the actuator doors are vacuum controlled and the vacuum source is lost, it may revert to defrost mode and stay there. The vacuum source, if that is the problem, should be located under the hood. I don't have a vac diagram right in front of me.
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Saturday, June 6th, 2009 AT 4:41 PM

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