Tick Under Glovebox
 

I recently purchased an 1986 190E that seems to be in very good shape. I have noticed an intermittent tick that comes from under the glovebox area. It seems intermittent while the climate control is on, but it also clicks when I touch the brake pedal. Is this a problem relay or something that sounds normal... Quite annoying regardless. Any suggestions?

There is a vacuum switchover unit behind the glove box that may be causing it. ?

Would a vacuum switchover cause a tick when the brake pedal is depressed..e.g... are the brakes or lights somehow operated through it?

LOL! Finally! Someone else is asking about this! My SD has/does the same thing. I found a "black box" down under the floor mat that the ticking comes from. It's under the glove box, mounted on the forward, almost verticle part of the footwell. Starts ticking when the doors are opened, ect as you say. Ticks for 30 seconds or so, then quits. It's quite a bit louder when you have the floor mats and underlying insulation out.
Have no freakin' clue what it does.:confused:

ON the W201 chassis this ticking is a common PROBLEM. The feed-back potientiometer for the blend-air door will get a bad spot & then you will hear this ticking from the switch-over valve group. YOU need a new feed-back resistor.

M.B. Doc,
Where is the potientiometer and the resistor? I have looked through the cd but have not seen this mentioned. I have some clicking and the flaps sometimes have a mind of their own but I have no leaks.

Ok.. so if I am getting perpetual heat from the outside vents, I can assume there is a vacuum leak and the noise is related. I'll ask again so I am clear.. this too would cause the same noise to happen when I press the brake pedal?.. I can't see the connection, but I am relatively new to this. I really appreciate the help.

Where is the feedback resistor located?:)

The reason you might hear a change when the brake pedal is depressed is, the feed-back pot is mounted on the blend air flap that is VACUUM controlled. If the vacuum is reduced then the FLAP will move changing the position of the potentiometer.

BTW the feed-back potiontiometer is at the top of the heater box & the COMPLETE dash must be removed for replacement.

M.B.DOC

I will shortly be replacing the heater core on my daughter's '87 190E 2.3. Your comment on replacing the potentiometer requiring the dash removal makes me want to ask what components should be done while I have it apart?

-Heater core
-Potentiometer
-???

Haasman