Drivers door mirror constantly hot( heated mirror) and now the glass is foggy

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New Member
Jan 5, 2013
C270 Cdi
Hi can anyone point me in the area to start solving my problem... I have a 2002 C270 Cdi estate elegance, I've noticed over the past couple of months that the heated mirror on the off side (drivers) is continually on as opposed to the near side which is cold, this as also caused the mirror to appear foggy so I near to replace it...
Could it be a problem with the Heater / Climate controller in the centre console, I've noticed that when I push the heated rear window button I get interference over the radio.... I believe the heated rear window and mirrors are connected........And I've just started having a problem with the heater fan... Sometimes it works, sometimes it doesn't
Can anyone recommend an Indi in the Reading / Oxford area.

Can anyone recommend a good indi in the Reading/ Oxford area ....
Heated mirrors are automatic (not related to other heaters), they go on when outside temp is below something (5C I think?)... continuously on may be caused wrong temp signal?

Heated rear window interferes with radio because radio antenna is also rear (don't know W203 for sure, W210 it is wired to the window too). Don't know solution, mine W210 does the same.

Heater fan may suffer bad 'pre resistor' unit, or simply fan control panel is misbehaving. Is the climate manual?
Climate control can be run in either manual or auto,(mine is usually in manual) yesterday on a short trip the fan came on from start then two mins later it stopped, stopped the car, upon restart he fan worked again.....temperamental or what.....
Are the heated mirrors independent of each other, hence why one is hot and the other not or is there a central sensor somewhere???
It might be different on a C Class but on the E Class the heated mirrors are activated when the Windscreen Defrost button is pressed I believe.

Mine too has a fault with the nsf mirror which is on permanently all the time the ignition is on.

This is down to the DCM (Door control module) which has a fault.

New module is £300 so it can stay faulty as it does no harm and doesn't cause any 'milking' or fogginess.

I believe BMW mirrors are heated all the time the ignition is on.
Early C and E class cars mirror heaters were permanatly supplied, and there is a thermostatic switch on the back of the glass, trigger point of this switch as mentioned above is in the region of 4-5 degrees.
The later 210 E class and later cars were I believed supplied directly from the DCM, and the temp info to switch on is taken from the CAN BUS. The temp. at which the later cars mirror heaters operate is higher and is in the region of 14 degrees. How and if they switch off I,m not sure (apart from temp. being over the trigger point).
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