So i buy a used 07 trailblazer for my son. It checks out great when i first looked at it.. now when picking it up we had to jump it ... dead battery. OK Dead battery, time to let the vent motors resync. Pull the fuse (39) and wait a few minutes. Put it back in turn key to on and nothing... start it and it clunks again for 30 sec before stopping. Never allowing air thru the front vents. BTW its not clicks.. its a loud clicking clunk sound right behind the left center front vent.

I need help to diagnose the issue and the easiest way to fix it.. thanks!

Ron

 

I had an 03 Trailblazer and never had to resync the vent motors after disconnecting the battery. You are hearing a mechanical problem probably a stuck actuator or vent door.

 

thats what i suspected but there were posts of re sync being needed after battery disconnection .. thought it would be easy but guess not.. Dam thing was fine the 1st 2x i tested it.. then i buy it and WTF..ugh