2001 GMC Sierra Air vent selection problem

Tiny
H1MACHIII
  • MEMBER
  • 2001 GMC SIERRA
  • 8.1L
  • V8
  • RWD
  • AUTOMATIC
  • 342,000 MILES
Hi,
When I select 'dash only' position on the vent selector knob something behind the dash starts clicking (about 2 per second). If I select a dash vent/floor vent mix (10 o'clock on selector knob or second position) there is no clicking. I removed one of the actuators (passenger side near center console and inboard of the motor and filter) opened it up and found no visible issues. I closed it back up and reinstalled it. I previously could not change vent position and didn't get air out of any vents but after reinstalling actuator I get air out of selected vents but clicking continues in the dash vent only position. Also if I have outside air selected and vent select knob in any of the defrost positions and I try to switch from outside to recirc, the recirc light ion button flashes and stays in outside air. That doesn't happen with other vent positions selected. Do I need to reset the HVAC system? I have read online that sometimes that corrects these types of problems but cannot find the reset procedures. Thanks for any help you can provide. You guys are awesome!
Wednesday, October 29th, 2014 AT 12:15 PM

1 Reply

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
It sounds like a bad mode door actuator I have seen plenty of actuators do that when they get to the stopping point of the doors movement one way or the other. The actuator slips and doesn't cause enough resistance on the actuator to shut it off. Seen it alot on recirculation door actuators. If the door is not broke the actuator is bad.
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Wednesday, October 29th, 2014 AT 10:02 PM

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