Outside air vent 'thumping'

2003 PONTIAC VIBE
75,000 MILES • 4 CYL • FWD
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CLARKHYV
  • MEMBER
  • 1 POST
Hear a small 'thumping' in dash (like tapping your hand on the dash) when push button to open outside air vent. Thumps 9 times, then makes other sound, then starts up again...9 times, then other sound. Repeats.

Stops when push button to close outside air venting. No other 'symptoms'. When run fan with outside air vent open (while thumping is going on), can hear air pulsating with each thump.

What would problem be? What would I be up against to get it fixed?

Thanks!
Jul 5, 2011 at 3:15 PM
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WRENCHTECH
  • ✓ASE Certified Mechanic
  • 20,761 POSTS
  • ASE Certified Mechanic
The recirculation door is vacuum operated and it sounds like it's losing vacuum somewhere. Use a vacuum gauge and test it at various spots. It should be equal to the manifold vacuum reading.
Jul 5, 2011 at 4:11 PM
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