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.

Doug

.

 

So why does it happen when the car is turned off

 

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.

 

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.

 

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....

 

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?

 

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

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

.

 

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

 

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.

 

2011 Impala I have, scared the crap out of me when it started doing this horrific noise!

 

My problem was the Passenger heat actuator.

 

Replaced all three actuators on my 2012 LTZ

It was a horrible noise, drove me up the wall. I replaced the one above the glove box on the passenger side (not terrible but had to pretty much do it blind because I could not see it after I had my hand in there. Took about a 1/2 hour. I paid a friend who does car work $40 to replace the two above and inboard of the gas pedal.

Really hoping the 9th gen Impala's do not have this same problem. Been in the back of my mind ever since I bought my 2014.

 

Ed, iirc, with dual climate control, there are 3 hvac actuators in the pass. glovebox area: rh temp, mode (vent) and recirc. Only actuator between the steering wheel and radio is the lh temp. All are the same part# except the mode (vent) actuator. Looking into the glovebox opening, rh temp is on the left, mode (vent) is atop the rh temp and the recirc is top right behind a large wiring harness. Lh temp is up under the dash between the steering wheel and radio accessed by removing black plastic kick shield. I've had to replace both temp actuators. 5.5mm (7/32"). $15/ea. on Amazon. Dorman part# 604-108.

 

Ed, iirc, with dual climate control, there are 3 hvac actuators in the pass. glovebox area: rh temp, mode (vent) and recirc. Only actuator between the steering wheel and radio is the lh temp. All are the same part# except the mode (vent) actuator. Looking into the glovebox opening, rh temp is on the left, mode (vent) is atop the rh temp and the recirc is top right behind a large wiring harness. Lh temp is up under the dash between the steering wheel and radio accessed by removing black plastic kick shield. I've had to replace both temp actuators. 5.5mm (7/32").

Sheila, you had to replace yours on a 9th gen? (2014-present body style):icon_shaking:

 

Sorry Ed, 8th gen., '12 LT. Also had to replace the rh (pass.) temp actuator on son's '16 LT Limited (old body style). All 3 temp actuators were $15/ea. on Amazon.

 

Well don't feel too bad about $340.00 to replace all 3 actuators. Some knucklehead here wanted $450.00. Needless he's still waiting.

 

i paid in the 300 dollar range i think for the two blend door actuators on the temp control. i bought the parts but didn't feel like standing on my head to change them...i felt the annoying clicking going away was worth that price lol.

 

You can check out blenddoor.com to purchase an alternate gear ($19) that the vendor claims is superior to the original gear that fails.

For my recent drivers side actuator failure, I purchased a new Dorman 604-108 actuator, opened it up, removed that gear that eventually fails and installed the blenddoor.com gear instead. Also lubricated it with the synthetic grease that comes with the gear. Although I could have just put the new gear in the old actuator, the whole actuator is cheap enough to replace.

Note that several models are sold on blenddoor.com so select the correct part. For my 2007 LT only the rebuilt kit that has a "larger gear on top of a smaller gear" will work. The aluminum gear, the white Delrin gear, and the black single gear (not "stacked") won't fit for my 2007. I don't know what year GM made the change where the gear (that fails) is pressed onto the shaft rather than manufactured as one piece.

 

While performing the 50K-mile service on my '16 Limited this past weekend, I had to disconnect a multi-pin harness plug from the inlet air tube so I could pull the tube to get the air filter box open. Apparently disconnecting that harness plug causes the HVAC controls to forget their positions, and I was treated to some horrific actuator racket as soon as I keyed the ignition after buttoning everything back up.

TIP: Forget about the possibility of just needing to pull the "Display" fuse in the engine bay fuse box once you hear that infernal clacking sound. All pulling the fuse will do is reset all of your DIC data, such as your trip odometers, average fuel economy, etc. (Pissed me off to discover that these aren't backed up in static RAM!) The clacking sound you hear means one of the gears in an HVAC actuator has broken off a tooth. And I'll bet you even money that it's the intermediate gear that has the broken tooth. It's the weakest link in the gear train inside one of these things.

But I digress. In my case, it was the recirc actuator that failed - the one near the right A-pillar, behind and to the right of the glove box. Amazon sells a number of different replacement actuators, and the AC Delco # 15-74122 is only a few bucks more than the no-name Chinese junk, so I bought a few of those, knowing that I'll eventually need them all. The Delco actuators are also cheap Chinese junk, but hopefully not quite as junky as their no-name counterparts. (Rubbing that rabbit's foot for all it's worth. )

My order was delivered Monday, and I decided to replace the failed actuator yesterday after work. Holy crap! It's damned near impossible to replace that thing without pulling the whole dash apart! Specifically, it's an incredible PITA to remove and replace those 5.5mm hex head screws because they face out toward the fender! Going in, I pessimistically estimated 30 minutes to complete the replacement. It took me two hours, but, in all honesty, half of that was spent trying to locate and retrieve first one of the screws, and then the socket when they dropped down inside there.

But all's well that ends well. The new actuator found home right away as soon as I turned the key, and there's no more clacking. For now. Still, I can't help wondering when the next one will go or why Generous Motors couldn't have spent a few more pennies to make those gears out of pot metal, UHMW, or nylon instead of what looks like 3D-printed plastic.

I split the case of the old actuator open to see where the tooth was missing, and am thinking of buying a rebuild kit from blenddoor.com to replace that gear, but it's difficult to justify $17 for one gear (THIS ONE) when an entire Delco actuator is only $26 from Amazon. Sure, the gear is described as being made from "tough engineering grade plastic," whatever that is. But it's still plastic. I'd feel a lot better about a nylon or metal gear - even pot metal - for my seventeen bucks.

 

Holy crap! It's damned near impossible to replace that thing without pulling the whole dash apart! Specifically, it's an incredible PITA to remove and replace those 5.5mm hex head screws because they face out toward the fender! Going in, I pessimistically estimated 30 minutes to complete the replacement. It took me two hours, but, in all honesty, half of that was spent trying to locate and retrieve first one of the screws, and then the socket when they dropped down inside there.

No doubt, it's a pain getting under the dash, looking up into dark, cramped space, then trying to reach into the tight places.

I have found some trick socket tools that help. Seems like, I used the flex screwdriver on the last actuator I replaced. It's super handy for stuff like this.

As for 2 hours, you must admit, working on your own car makes you realize that maybe some of those outrageous garage prices aren't really so outrageous

As for repairing the actuator, it's not that far fetched. Years ago, I opened one up (off my 07 SS) and saw the damage on slow moving gear(s). I was able to re-position the damaged teeth such that they were never engaged by the mating gear. It's been working fine in the car ever since

BTW, a 7/32" socket is pretty danged close to 5.5mm, altho I have both

Doug

[Edit]That pic makes me look ape-hairy

.

 

Fwiw, for those on a budget, Harbor Freight Tools offers a 3-pack (1/4", 3/8" and 1/2") for cheap.

 

I had to change the module in my car this past summer. The on nearer the firewall behind the glove box. That's the tough one. And the tapping would start when I unlocked the car, and go on for a while after I shut it off.

NOW, I hear tapping when adjusting the heat cold or hot.....?? Where is THAT Module?!?!?!

 

Tony, do you have dual hvac controls (driver/pass.)? Can you tell which side of the dash is tapping? Driver temp bda is ~ above the gas pedal. Pass. temp bda is behind the left side of the glove box.