In my never ending battle with the ticking from what seems to be behind and between the radio and glove box I have now figured out that I can temporarily get the offending servo to stop ticking if I have the temperature low and move it up about 15 degrees, such as from coldest setting to 75 degrees. Running through the blower mode or changing from recirculate to fresh air does not stop the ticking even for a moment. My air does blow properly at all modes and I do not yet have any problem with temperature. Just the intermittent ticking.

Is this proof positive that the offending servo is indeed the air mix servo?

 

Yup, sounds like the air mix servo.

My air mix servo makes noise during the summer time, presumably because it's set to lower degrees. I rarely every hear a ticking during the winter since temp is usually set higher up. I will eventually do something about it, but it works fine and only makes noise occasionally so it is only an annoyance.

 

I also get occasional noise during the summer. I pulled the glove box this summer, to check out the effort to repair/replace. I didn't pull the servo or clean it, but I tapped it a few times with a screwdriver..and go figure..no more noise so far.

 

If I turn on the car and everything else is off (no AC, no heat, no return air, no fan, etc), why would I still hear that damn clicking noise?

 

Because the servo is still trying to move into the correct position from what the HVAC was last set to. My particular servo that's gone bad is the air mix servo, so I turn on the fan and run the temp up to "heat". And then shut off the fan since I don't want warm air blowing at me. The noise will then be non existent, because the servo is already in that postion at least in my case. You may have to change the temperature in the other direction in order for it to stop making that noise, depending upon where the servo is stuck.

If it's one of the other servo's making noise, you can change the mode, recirculate, etc. in order to stop the noise. Just cycle through the functions and eventually the noise will stop and you will know which servo it is and where it is stuck.

 

There is air flow at low level.

Salim