Very odd car question

RL1

Member
May 20, 2010
1,649
Ga
I was getting out of my patrol car (07 Impala) for lunch today and heard a very odd noise about one second after I turned it off. It sounded like something was thumping behind the air bag and neither me nor my sgt could figure out what it was. The car ran fine, all the gauges were in the norm, didn't even make the noise when turned on or driving, though every time I turned the car off for the rest of the afternoon, it did it. After trying out a few things, I figured out it would only happen when the ac was turned off, either manually or when turning off the car. I played around with it some more and found what was making the noise. When I would turn the ac on, there is a thing I can only describe as a plunger that moves upward and out of sight (I am only able to see through the half inch gap between the back of the glove box and bottom of the dash). When the ac goes off or is turned to defrost mode, the plunger moves back down and appears to get caught on something and not seal/lower fully. It will then still try to move down for about 45 more seconds, making the thumping nose, before finally stopping. I know it has something to do with the ac and am assuming there is something that is blocking it from returning to it's usual spot. Does anyone have a better guess as to what's causing it and how to fix it without ripping out the glove box?
 

BigDogg795

Member
May 21, 2010
386
Long Island, NY
Nah, pretty sure my impala and my silverado before it both made similar noises...something about the directional doors resting after power gets cut off (when you turn it off)...


If it works, does it really matter anyway? :)
 

RL1

Member
May 20, 2010
1,649
Ga
I'm not a fan of the noise since we have to run the defroster a lot on night shift with all the humidity we have. Also don't want extra noise if I am getting out of the car and trying to be quite (also turn the car off so the fan won't kick on).


crescentstar69, I asked but no one at the dept seems to know... I asked if I could take it to the Chevy place but was told to take it to the city shop (the same place that fried my CVPI's computer and spilled coffee in my digital camera system when I sent it in for a new headlight harness).
 

ryanm

Member
May 20, 2010
587
Arkansas
The solenoid that operates the door on something in that ventilation system (fresh air intake, maybe? blend door? not sure what it's called) is known for going bad and doing exactly this (so I've heard from departments with Impalas).


Some of them get stuck in a cycling mode for more than a few seconds and make quite a racket.
 

hfd163

Member
May 20, 2010
74
Rochester, New York
My car did the same thing 2 days ago, If you open the glove box and look behind it you will see it trying to close the vent when the defrost is turned on. Easy fix is right on the right hand side of the vent box behind the glove box you will see and electric plug, unplug it and it will work just fine for you. PM me if you have any questions about it or need some pictures.
 

RL1

Member
May 20, 2010
1,649
Ga
Hey guys, thanks for the input. It was the defrost vent door thingy and the store happened to have a motor for it in stock so it's fixed now (and I've not noticed anything else broken...yet).
 

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