W202 Erratic Climate Control

[angus falconer]

My climate control is acting oddly. It basically seems to alternate between hot and cold without much in the middle.

If I want to cool the car down I hit the "down temperature" button and, say, get it down to "18 degrees" and it pumps out loads of cold air. It will then continue to pump freezing air out ad infinitum. I then try to find a more sensible temperature and repeatedly nudge it up a couple of degrees at a time a few times and nothing happens until I get it, say to "24 degrees" or something and it starts blasting out hot air. Again it will continue to blast out hot air until I go the other way again.

So, basically the air con works but the climate control function doesn't.

Any ideas? I took it to BSG and they couldn't trace the fault.

Should I take it to an air-con specialist and if so does anyone know a good one in north or west London?

 

[television]

Could this be the Duo valve sticking Angus

 

[angus falconer]

W202 - locaction of a/c cabin sensor?

Could this be the Duo valve sticking Angus

Thanks Malcolm

After looking through the various "duovalve" posts I think it may be either

(1) the "monovalve" (my a/c isn't sided)

(2) the cabin sensor

Hibbo offered the following advice in another thread and I now recall BSG suggesting the same thing;

"It sounds as though the cabin temp sensor isn't working properly, so the heater can't compare the actual temp to the set temp. On the w124 there's a little vent up in the interior light/sunroof switch bit in the roof that sucks cabin air in to detect the temp. If this gets clogged up with fluff etc this can cause the heater to malfunction."

So now the question is; where is the cabin sensor in a W202?

Angus

 

[G MAN]

i believe it is in the interior light cluster on the roof, this side of the rear view mirror, & is either one vent or two smaller ones if you have a sunroof switch in the centre.

 

[MotardMan]

Cut out a square of paper slightly smaller than the sensor vent in the interior light. Turn on the ignition or start the car and hold the paper on the vent. When you remove your hand, the paper should stay on the grille.

 

[angus falconer]

Thanks Gman and Motardman

I can see the grill now.

I'll try the paper test when I get a minute

Angus