View Full Version : Clicking noise from HVAC system

11-20-07, 05:31 PM
Hi all,

Hoping someone can help me diagnose this problem. Just got my V (2005 9900 miles) and love it. Can't really drive it yet though, need to pass inspection, etc still.

Anyway, I'm having a problem with the HVAC system. First trip, no problem, stopped at the store, when I got back in and started the car I got this loud clicking noise coming from behind the Nav system somewhere. When I turned the passenger side hvac on it went away for a couple seconds then came back. I turned the hvac off, noise went away, turned it back on and it came back. Switched to defrost, then back to auto and it went away and didn't come back.

The noise sounds like maybe a gear clicking/slipping or something. It's a pretty loud noise.

Any ideas?


11-20-07, 05:53 PM
Could be this:

Interior - Snap Pop Noise From Lower Winshield Area

Bulletin No.: 06-08-49-005

Date: February 16, 2006



Snap/Pop Type Noise Coming from Instrument Panel or Windshield Area (Modify IP Retaining Slots and Replace Mylar Tape)


2003-2006 Cadillac CTS
2004-2006 Cadillac CTS-V, SRX
Some customers may comment on a snap/pop type noise coming from the instrument panel or windshield area. The noise may be more pronounced when the vehicle is cold and the HVAC defroster mode is selected.
A slip-stick condition may occur between the six retaining fingers for the defroster grille assembly and the plastic slots inside the instrument panel carrier.
Verify the customer concern before attempting the repair. It may be necessary to operate the vehicle's HVAC system in the defrost mode to duplicate the noise. If the noise is present, perform the following steps:


Remove the defroster grille from the IP.


Using a flat-bladed tool, pry upward on the grille in order to release the retaining fasteners.

1.2. Disconnect the sunload sensor wiring connector.


Inspect the mylar tape that is attached to the six plastic retaining fingers (1) at the leading edge of the defroster grille. If the tape is deformed, torn or worn, replace the tape with new pieces of mylar tape, 3M(TM) Squeak Reduction Tape 5430, or equivalent.


Locate the six slots (1) on the IP where the retaining fingers for the defroster grille would be inserted.

Remove the small tab (1) inside each slot of the IP. The tabs can be removed with a knife or file.
Install the defroster grille to the IP.
Connect the sunload sensor wiring connector.
Line up the retaining fingers and fasteners and push down to seat on the IP.
Road test the vehicle to verify the repair.

11-20-07, 06:21 PM
Thanks Darkman, I don't think that's it though. The noise went away when I put it in defrost mode.

The noise was happening on Auto mode but I didn't go through the different modes to try to isolate which was the problem (ie. defrost, vent, floor), will do that tonite.


11-21-07, 01:35 AM
Where is the fan blade (squirrel cage) located? If its a little off it could be the source. Or, if a piece of paper got sucked into it.

11-21-07, 08:20 AM
Any time I ever had that type of thing in one of my cars, it was leaves or other debris that had gotten into the air ducts...you would be surprised at what can get down in there. Look on the FAQ about how to change your cabin air filter (or take it to the dealer) and see if you can see or dislodge something from that end. The fan isn't binding up when this happens, right?

11-21-07, 03:43 PM
I'm not sure how the "doors" inside the system are opened and closed to change the airflow from vent to floor, etc. but it sounds like maybe there's a motor that opens/closes the door and the gear on it is stripped. Or maybe one of the doors is coming in contact with the fan.

It seems to be blowing air fine even when the noise is happening.

The noise is pretty loud and it's a rapid clicking sound. Kind of reminds me of the sound a starter makes when the battery is almost dead and not strong enough to turn over the motor, just rapid clicking.

Thanks for the ideas so far guys.

11-22-07, 07:13 PM
Just another update, I've determined that the sound only happens when I try to switch to the vents. The noise doesn't happen on defrost or floor modes. So I'm guessing that there is a door that opens/closes to guide the air to the vents and there's either something stuck in there or the motor/gears are stripped.

Next question is: if I pull the Nav system will I be able to access the hvac with enough room to open it up and take a look? Anyone know where I can get a diagram of the system?


06-03-08, 04:08 PM
Just wanted to update everyone on this. I don't have warranty so took on the job myself. :cookoo:

Spent 6 hours dismantling the entire dash in the car. Got the point where all that was left was the cast aluminum frame that everything bolts to. Of course all of the HVAC components (heater box, etc) are located behind this frame with no way to access them. I undid all the bolts but could not get the frame out so ended up cutting a hole in it to access the actuator motors on the side of the heater box. Ended up that one of the tabs on one of the door flaps had skipped out of the cog that is attached to the actuator motor. Not sure how that happened but it was causing the actuator motor to bind and wasn't allowing it to open and close the defrost flaps all the way. So the source of the clicking was the stuck motor once it hit the point where it was binding.

Definitely not something I'd want to do again, about halfway through, (while the entire contents of my dash were strewn around the garage) I started to feel ill just looking at the state of disassembly. :drool:

Just in the process of putting it all back together and hoping that I don't have any left over parts...


06-03-08, 05:38 PM
Did you get any pictures of this carnage?

06-03-08, 09:35 PM
Thats called exploratory surgery. Sounds like you just attained your advanced degree. Sneak any mods in while you had the dash out? Someone changed the lightbulbs behind the guages. Gotta love this forum.
Pics would be awesome.

06-04-08, 08:34 AM
Did you get any pictures of this carnage?

Thats called exploratory surgery.
"For re-assembly simply reverse the procedure used for disassembly"

:bonkers: :bonkers:

06-04-08, 12:34 PM
Yup, that's pretty much it OldRoadDawg. Though I didn't quite get to that level of disassembly but pretty close.

Unfortunately the batteries in my digi-cam died so I didn't take any pictures. I was kind of in a rush to get it back together as well cause I didn't want to forget where anything went. So, no additional mods either unfortunately.

After finishing the re-assembly last night I had no left-over bolts or screws so that made me feel good. Drove it to work today and no problems other than a slight rattle over large bumps. Thinking I might have left a socket or something behind, oops.

Also, noticed my rad has a small leak so looks like the next mission will be replacing it. Oh yeah, and the rear diff is weeping a bit of fluid as well. :crying2:

06-04-08, 04:53 PM
Wow! Look at that disassemble! I have have the exact same problem. I have two actuators 'grinding'. One when I start the car and one about 20 seconds after shutting it off. It definetely sounds like plastic gears stripping. Hey, how hard was taking the gauge cluster out? I was hoping to get to the actuators from under the dash - no? I am about to venture in tonight. I'm replacing the whole dash harness so I'll tackle those actuators while I'm in there. any tips on what NOT to do while taking the dash apart?? - thanks. "still fixin the salvaged V.."

06-04-08, 07:21 PM
Sounds like the exact same thing I had though mine only happened when trying to turn it to vents only or vents+defrost and then it also happened about 30 or so seconds after turning off. After turning the car on and off with the dash apart I could see that the car adjusts all of the heater flaps to some preset position about 30 seconds after turning it off.

You definitely cannot get to the actuators by just taking the cluster out. Though now that I cut the piece out I can now access the actuator enough that I would be able to fix it again if it popped out again just by taking the cluster out. The cluster is really easy to get out. Just take the plastic around the column off, then the plastic cover that butts up to the bottom of the cluster just pops up and off, two bolts at the bottom of the cluster, then using a wide-ish flat screw-driver or similar, pry between the top of the cluster and the dash. The top of the cluster has 3 tabs so looks like _____--____--_____--_____. You need to pry the dash up over the tabs as you're gently prying out. Hopefully that makes sense.

You can get to the temperature actuator from underneath the dash but not the mode switching ones. There are two mode actuator motors. To access them you need to pull out the entire dash (cluster, radio, hvac, etc) and the entire sub-frame underneath (cast aluminum). Or, you could cut a hole in the top of the sub-frame to allow access to the actuator motors underneath, which is what I did. I cut about a 4x4 inch hole using a dremel tool and it took about an hour.

As for tips...
- make sure you drop the steering linkage, no need to remove the steering wheel though, makes it way easier to get the dash out
- be careful around the airbags - if you end up pulling the entire sub-frame then you will have to disconnect the driver side airbag for sure
- I couldn't get the subframe out, I unbolted every bolt I could see, and even some I could only feel that were up along the firewall, and still couldn't get it to budge, not sure what I was missing
- make sure you remember where all the nuts/bolts/screws go or try to keep them in piles near where you took them out
- don't push/pull on the door flaps inside the heater box, I broke one and it was a pain to fix, they're quite fragile
- take your time to figure out how each of the connectors comes apart, they're all different and come apart differently
- the speaker in the center of the dash is easier to take out and disconnect before you start to pull the main dash apart, so once you pull off the defroster cover then take the speaker off and disconnect the connector
- be careful with the clips on the arms that hold the glovebox door on, they have a clip-type connection where they attach to the door and you have to push in the tab while pulling it out. not sure how to explain better but I broke one of the little tabs by pulling too hard without the tab being pushed in far enough.
- I was able to connect the battery, turn the key on and test the hvac system with everything apart. I did have to re-plug in the hvac control obviously, and I didn't disconnect any of the connections to the steering column. There are also two connections on both ends of the dash, right behind the end covers that I also had to have plugged in.

In total I spent about 5 hours taking everything apart, about 1 hour cutting, 10 minutes fixing and re-greasing the cog on the actuator, and then about 3 or 4 hours putting it all back together.

Good luck!!

BTW, my car was a salvage title car as well so that's why I have no warranty. It was repaired before I bought it though. It's an 05, only had 9K miles and I paid $22K for it last year. I love the car and obviously am prepared to fix whatever I can myself. It's been a great car so far.


06-05-08, 11:31 AM
Hey thanks for the info man! Nice to have a few little tips. You are dead on about connectors. All different and most a pita. I have stripped out the entire interior except the dash. I have replaced everything electrical except the dash harness which is what I'm going after now. The car is a Katrina salvage. It's been a total nightmare project - one I'll never do again. I'd rather buy a wreck and straighten it than mess with an electrical nightmare like these cars. My dash will soon look like your picture so your info is helpful. Do you know how many clips, connectors, ties ...etc that I've broken trying to tear everthing apart? PITA. The actuators that I can reach from under the dash are loose? The previous owner attempted to fix them and didn't put one of the screws back in. There are two actuators making noises depending on which controls I push - same as you explained. So what did you do to fix them? Take them apart and lube?, clean, adjust?
I wish that huge aluminum brace could come out. Sure would make snaking the new harness all over the place easier.
The only good news with this car is the previous owner replace the block and heads with an LS2 and kept the better flowing LS6 intake ...etc. And he put a cai kit in. I got it tuned by a well respected guy here and it is amazing. He dyno'd it at 359 rwhp & tq. That's more than I've seen LS6's have with headers and exhaust. So driving it is awesome but looking at all the work ahead of me isn't - it's a good thing I like to fix things...... good luck.

06-05-08, 12:07 PM
Wow, yeah, definitely don't want to get into fixing electrical issues, ouch, hope it works out for ya. Sounds like it will be pretty sweet once it's done though.

I couldn't get the aluminum brace out but there's obviously a way. From what I could see you have to pull the e-brake and clutch assemblies as well because there were a couple of bolts that I couldn't get to with those in the way.

As for the resolution to my clicking; if the actuator is clicking then it's working fine, you shouldn't have to pull the actual actuator apart. Each of the actuator's has cog-type thing attached to it which has slots in it. Then the door flaps have a nub that rides in the slots on the cog. In my case one of the nubs had jumped out of one of the slots so when the motor was trying to turn the cog it was hitting the piece that popped out and wouldn't let it move any further. If you look up under the dash you can see/access the temperature actuator. This will give you a good idea of what I'm talking about with the cog/slots/nubs, hahaha, my "technical terms" might not be that helpful.

Good luck,