Automatic dimming rearview mirror not working - PeachParts Mercedes-Benz Forum

F18 · #1 10-02-2008, 10:30 PM

I have been meaning to trace this problem with the rearview automatic dim function but it was not high on my list. But now that it is getting dark earlier I am spending a fair amount of time on the road after dark.
When I first bought the 98 E300 the rearview mirror would dim automatically when the headlights of a car approached from behind at night. It has not worked for at least a year. The mirror cannot be dimmed manually with a lever.
Any idea of how to trouble shoot the problem?.....I have checked fuses but that is as far as I got!

THANKS

babymog · #2 10-02-2008, 10:58 PM

Is it turned on? I believe that the 210 mirror has an on/off switch on it.
The mirror runs from the overhead switch power, if they work properly when the key is on, should be good there. There is also a reverse inhibit circuit, if the car is in reverse, the mirror dimming is inactive. It's about all I remember of that mirror, been a long time ago.

F18 · #3 10-03-2008, 11:27 AM

babymog...thanks for the reply.
That was the first thing I checked for was an on/off switch that I might have tripped when cleaning the windshield. But there is no switch anywhere on the mirror.
There are two sun light sensors....one in the bottom right corner of the mirror and on the back side of the mirror housing facing forward. I am suspecting one or both of those little 1/4" round sensors are bad. They are the same sensors on my outdoor solar lights and security lights around my house....and they don't last more than a few years exposed to hot and cold temps.

I'll have to pull it apart and put an ohm/volt meter to it.

Thanks again!
Cheers

TMAllison · #4 10-03-2008, 12:35 PM

I may be wrong but I believe one of those sun sensors may be the garage door transmitter.

I've noticed my mirror dimming much, but, I do have VERY dark tint on the rear window which may be the reason.

babymog · #5 10-03-2008, 12:41 PM

We designed and built those mirrors, millions of them, and it is extremely rare for them to fail electronically.

If it were my mirror, I'd look at power supply and reverse-inhibit wiring. Does your manual say anything about it? Does the homelink still work?

F18 · #6 10-03-2008, 01:26 PM

Well then the next thing to do is to check for power at the mirror and work backwards. It was a nice feature when it worked! Now I find myself just turning the mirror away or up to keep the blinding headlights from behind hitting my eyes....not good!