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post #1 of (permalink) Old 11-05-2018 Thread Starter
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tapping noise under dash

There is a tapping noise coming from under the dash when my 2010 Impala LT is NOT running. This noise stops in a few minutes after starting the car. Then it starts up again.
I haven't opened the hood yet to look more closely but do you have any ideas on what could be making this tapping noise?
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post #2 of (permalink) Old 11-05-2018
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Originally Posted by cchamm62 View Post
There is a tapping noise coming from under the dash when my 2010 Impala LT is NOT running. This noise stops in a few minutes after starting the car. Then it starts up again.
I haven't opened the hood yet to look more closely but do you have any ideas on what could be making this tapping noise?
This is a common issue. The air conditioner/heater has several damper actuators for controlling hot/cold , vent selection and inlet selection (fresh air/recirculation). When they fail, which is not uncommon, they will make an annoying popping sound. This is usually due to a stripped gear inside.

They cost around 35 dollars plus labor to replace, which often takes the job over 100 dollars.

With the ignition on, and AC fan on low, try adjusting your hot/cold knobs, one at a time, to see if the noise starts. Then try selecting recirc. Next try selecting a different vent (feet, face, defrost). The idea is to identify which control causes the noise to start. That indicates which of the 3 or 4 actuators need replacing.

With that knowledge, you should be in good shape for getting it repaired without getting ripped off.

HTH.

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post #3 of (permalink) Old 11-05-2018
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at 170k miles i just had both temp blend door actuators fail. the parts were about 25 each on rockauto but after watching the videos of how to do the work, i decided to take it in to the shop. 340 later the noise is gone...110 for parts roughly, the rest in labor. if it's the driver temp blend door you have to remove the lower part of the dash. getting to them isn't too terrible but getting the parts in/out are the pain from what i've read/seen. plenty of posts on these forums regarding the blend door actuators for further information.
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post #4 of (permalink) Old 11-05-2018
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Damn $340!!!

Man, if I were closer I would've did that job for way cheaper haha.
Luckily I have small hands so it is a little tight in there but I can usually knock these out within 30-45 mins.

I did a passenger side blend door not too long ago for a friend for $70. Took all of 15 minutes for that one.
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yeah, it's been a rough year with the 2010. 2600 for a trans rebuild and motor gaskets. then these actuators started going out. it was either pay to fix it or move on to a truck, the 340 was cheaper lol. i figured it was high priced on that job, but at least it isn't constantly clicking every time i get into the car now....
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Originally Posted by 2007Imp850 View Post
Damn $340!!!

Man, if I were closer I would've did that job for way cheaper haha.
Luckily I have small hands so it is a little tight in there but I can usually knock these out within 30-45 mins.

I did a passenger side blend door not too long ago for a friend for $70. Took all of 15 minutes for that one.
You know what they say about guys with small hands...

They fix things cheaper.
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post #7 of (permalink) Old 11-05-2018
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Just had this issue start with our 2012 over the weekend. Seems weird it will continue after the car is off and had concerns it might run the battery down, and would start randomly after closing or opening the doors. Kinda annoying while driving. In our case confirmed it was the blend door actuator by unplugging it, just a plug that slides off. Very easy to get to it to unplug it through the glove box door, you just pry the two tabs away and pull down on the door and the actuator is inside on the left. That part is $24 at rock auto for the delco oem. I had to order a fuel pump for my truck, so just ordered an actuator at the same time and used a 5 percent off code.

Cannot imagine how any shop could justify charging someone $340 for a repair for this part?

My 6 year constantly asks why. What adults can learn from 5 and 6 year olds, to listen with your ears and mind open. Hard to learn when you don't listen ......
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post #8 of (permalink) Old 11-05-2018
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Originally Posted by 12 lt View Post
Cannot imagine how any shop could justify charging someone $340 for a repair for this part?
Keep in mind, that was for two. If it makes you feel any better

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Seems weird it will continue after the car is off...
Here's my theory on that. At some point, the computer in the AC controls detects that the motor doesn't come to a stop when expected - the computer doesn't see the motor current go up like it will when the motor stalls which it should do when the damper reaches its travel limit. So the computer sets a flag to remind itself later to run a re-learn on that motor/damper combination.

After a while, when the computer detects the car is off, it sees the flag and attempts to do a re-learn on that motor. It begins driving the motor expecting to see the motor current go up when the damper reaches its travel limit. Instead, when the damper gets to its limit, the stripped gear begins slipping, and with each revolution, you hear the tap noise. All the while, because the motor is still turning - it has not stalled - there is not enough current surge for the computer to detect stall. Hence, it keeps sending power to the motor until eventually the re-learn routine times out. Until then, you keep hearing the annoying tapping sound, which then resumes next time you unlock the car

Doug

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post #9 of (permalink) Old 11-05-2018
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Quote:
Originally Posted by plano-doug View Post
Here's my theory on that. At some point, the computer in the AC controls detects that the motor doesn't come to a stop when expected - the computer doesn't see the motor current go up like it will when the motor stalls which it should do when the damper reaches its travel limit. So the computer sets a flag to remind itself later to run a re-learn on that motor/damper combination.

After a while, when the computer detects the car is off, it sees the flag and attempts to do a re-learn on that motor. It begins driving the motor expecting to see the motor current go up when the damper reaches its travel limit. Instead, when the damper gets to its limit, the stripped gear begins slipping, and with each revolution, you hear the tap noise. All the while, because the motor is still turning - it has not stalled - there is not enough current surge for the computer to detect stall. Hence, it keeps sending power to the motor until eventually the re-learn routine times out. Until then, you keep hearing the annoying tapping sound, which then resumes next time you unlock the car

Doug

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Interesting theory. Thought it was strange that it would only seem to happen when the car had some type of jarring incident, trunk open/close, door open close, timing was too immediate for it to be coincidence. Not sure if it ever took place with the door lock/unlock, but it quit after unplugging the plug to the actuator that is accessed through the glove box.

I don't know where the other actuators are at, but this one seems relatively easy to get to. I should have the part in later this week. Looks like 2 small bolts holding it.

My 6 year constantly asks why. What adults can learn from 5 and 6 year olds, to listen with your ears and mind open. Hard to learn when you don't listen ......
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post #10 of (permalink) Old 11-05-2018
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Originally Posted by 12 lt View Post
Looks like 2 small bolts holding it.
IIRC, they're specified as 5.5mm. But I'm pretty sure a 7/32" will work just fine

Doug

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post #11 of (permalink) Old 11-07-2018
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Originally Posted by plano-doug View Post
IIRC, they're specified as 5.5mm. But I'm pretty sure a 7/32" will work just fine

Doug

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Yep, a 7/32 1/4 dr with short extension on a shorty ratchet had this being a 5 minute job to change the one that was bad in our car.

While in there I did see two other actuators, the one on the right side did not look just terrible to get to, although would definitely be easier for someone with small hands which I do not have. The one on the left that is up under the dash was more difficult to see but did not try sticking my hands in there.
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My 6 year constantly asks why. What adults can learn from 5 and 6 year olds, to listen with your ears and mind open. Hard to learn when you don't listen ......
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post #12 of (permalink) Old 11-08-2018
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I fix them myself two months later I had to disconnect my battery to do something on to my car reconnected the battery ..the noise came back
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post #13 of (permalink) Old 11-08-2018
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My wife replaced both on each Impala and bought them from Rock Auto for about $20 each. It took her 15 min. per actuator...
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post #14 of (permalink) Old 11-09-2018
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Originally Posted by Joelmateo View Post
My wife replaced both on each Impala and bought them from Rock Auto for about $20 each. It took her 15 min. per actuator...
i have the parts, just not the time to work on them lately. that's why i went to the shop...and it was getting to a point where the window wasn't defrosting when i needed it to lol.
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post #15 of (permalink) Old 11-09-2018
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2011 Impala I have, scared the crap out of me when it started doing this horrific noise!
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