Strange sound under dash

[Longtalltechsan]

I might have an idea what this is from but it never sounded like this before. Awhile back (3-4 mos?) I had a clicking sound under the dash whenever I switched the vent from dash to floor or defrost. I replaced the mixer module and it went away. This morning this started. Totally different sound, but the same area. It happens when I unlock and open the door before the vehicle even starts. It also happens when I push the button to change the vent. It lasts about 15 seconds or so. Is the vent mixer module again? Or something different? It sounds like plastic being twisted or something like that.

Dropbox

www.dropbox.com

Hopefully the video link will work and what I'm experiencing can be heard.

Thanks in advance.

 

[99WhiteC5Coupe]

I might have an idea what this is from but it never sounded like this before. Awhile back (3-4 mos?) I had a clicking sound under the dash whenever I switched the vent from dash to floor or defrost. I replaced the mixer module and it went away. This morning this started. Totally different sound, but the same area. It happens when I unlock and open the door before the vehicle even starts. It also happens when I push the button to change the vent. It lasts about 15 seconds or so. Is the vent mixer module again? Or something different? It sounds like plastic being twisted or something like that.

Dropbox

www.dropbox.com

Hopefully the video link will work and what I'm experiencing can be heard.

Thanks in advance.

One or more of your HVAC system actuators are defective. When the reach the end of their travel-limit, they can start clicking and strip the gear inside the actuator.

Some are easy to reach - some require partial dash disassembly.

You can disconnect the negative battery cable, then reconnect it and start the vehicle. Turn on the HVAC system but do not adjust anything. It will self calibrate the actuators in about one minute.

If the actuators are out-of-range, the self-calibration MAY eliminate the clicking if the calibration works. If not, you will have to have it service. Note that disconnecting the battery will erase stored trouble codes, including any for the actuators.

There are several posts on this forum regarding the matter. You may want to do a search and some reading.

It always helps others if you list the year, make, model, trim line and HVAC system type - as others may have year-specific information.

 

[BigOleFordFan]

Sounds to me like either:

A) A pump or motor of some sort struggling to start revving up, or
B) An actuator of some sort slowly moving into an open/closed position, or
C) Something slowly heating up to it's normal operating temperature...

seeings how it happens when you push the vent button, I would check the blend actuator door, since I had a similar sound in my 011 a few years ago and replacing that fixed it....