Auto Dimming Mirrors dark in daylight

[Satch]

Pretty much what it says on the tin: were misbehaving sometime OK but tending to go fully dark at random. Sticking finger over sensor corrects problem but returns soon.

Sensor problem I would think. Easy to fix?

 

[Dieselman]

Front facing sensor on interior mirror sensing darkness.

 

[tabbywrench]

I have the same problem on a 2005 W220, but putting my finger over the sensor does nothing. Anyone know how the rectify this problem

 

[DennisTheMenace]

could be a dry joint or failed sensor. replace the mirror or if handy with the soldering iron replace the sensor

 

[C43AMG]

New Mirror.

My Interior + Auto Dim door mirror both went at the same time, both blacked out. No one had ever heard of that happening before !!

I wont tell you how much a Auto Dim Glass cost or the Interior Mirror for that matter.

 

[jamie8954]

Quick question are both the mirrors supposed to go dark ? only my drivers side does not sure if passenger is faulty ? c320 w204

 

[Major774]

Passenger side is heated only.

 

[jamie8954]

Passenger side is heated only.

Thanks

 

[richard]

The external mirror (driver side only, although on new ML etc its easy to make the passenger side one do this by changing the expensive glass) is controlled from the sensors in the inside mirror. On factory fit (with the exception of old A/B class) you get both interior and exterior mirrors as one option.

So if it fails, both mirrors dim (or don't dim).

The exterior glass needs power do dim it (its electrochromatic), so I can't see how it can fail dimmed - its being told to dim by the door controller, which is being told to dim by the dimming mirror telling the OCP. (on reasonably new cars)

 

[mercmercmerc]

I had this on my 2004 211. drivers & interior mirror dark in daylight. Putting my hand over interior mirror ( not just finger on sensor as light gets round ) made them much lighter. Solved by opening interior mirror ( flat screwdriver in join but easy to mark ) and then cutting the wire to the rear sensor - easy to see and uninsulated ( the one that shows as a dot in the mirror glass ) be careful not to lose the clear Perspex rod that gets light from the front facing sensor as it drops out. I now have clear but non auto-dimming mirrors.

 

[whitenemesis]

Less drastic and easily reversible would have been to disconnect the RVM from the OCP by pulling the plug?

 

[tabbywrench]

I had the same problem and a friend fixed it for me. The sensor runs from front to back and can become loose and this broke a soldered joint my friend just resoldered the joint

 

[bigshineybike]

EEEk, I didnt even know they were supposed to do this feature. My W203 2006 driverside mirror is sort of bronze looking and not easy to see in the dark. I bought a new mirror from a 'mirror specialist' its lovely and silver but not got enough connectors to fit my car.
Having read the above I know why.
since I dont feel the need for dimming mirrors is it ok to rewire leaving off the electrochromatic bits? or does this upset other parts of the car?

 

[bigshineybike]

Just an update. its a few months later. The clever computer doesn't seem to have noticed that the special mirror is missing. All is well