98 Voyager 3.3L: There's a knocking sound behind airbag in the passenger side every engine start or key is inRUN of the ignition. The sound (tok tok tok tok)is like tapping a plastic with blunt object. Is there a ventilation flap that needs to move (close or open) when power applied? I removed the glove compartment but all I saw was black plastic encasement of the AC and no moving parts. I heard and felt the sound radiating to the plastic encasement. Any idea what I need to look or lubricate? Thanks for the help.

 

My 97 GC did that too.
Get on your back on the front passenger side floor with a flashlight
Behind the Glovebox there is a big plastic air handler box.
On the bottom of the air handler is a electric damper for the controlling the passenger air vent.
Watch it when you turn the ignition ON.
On mine the plastic gearing was turning past its normal range of motion. Making the pop noise you hear.
You maybe able to realign the gearing arm and get it to work.
I replaced it for $10 at the salvage yard.

Good Luck

 

Thank you. I was just in the junk yard yesterday trying to learn what's causing it by disassembling the same model. It was too hot and too much screws to remove so I gave up.

I will follow your advice and I'll get back here for result or fix.

 

You're right, its the gear/motor (actuator) that open/close the flap. I removed, opened and inspected it and found two teeth of the plastic gear was broken. It cost $80 at the dealer.I will get replacement from the junk yard instead.

Thanks for the accurate and direct troubleshooting advice. Well done.

 

Glad to help.

Tom

 

For future reference to some who may expereince it: Fix by replacing the the actuator located here per vangonebuy - "On the bottom of the air handler is a electric damper for the controlling the passenger air vent" . Cost me $5.00 (actuator,25 lug nuts and rubber tubing - for the vent drainage) from junk yard.