Mine never dimmed since I've got the car, so today I decided to take it apart for a closer look. It turns out the bigger of the two resistors had burnt out(3.9Ohm 1W), so I bought a replacement one for 2$ and now it works like new.

I'm not sure if it's just me or a more common issue, but I'm gonna post it anyway since it's a much cheaper fix than the 300$ new mirror...

 

great job !

 

Thanks for the heads up. Mine is not dimming so you have inspired me to take my mirror apart. Any tips on how it comes apart, would be appreciated.

 

Does yours have two lights and an infrared receiver at the bottom, if so you need to remove it first, by gently prying it off(it holds on by 4 hooks 2 in the front half - 2 in the rear, pointing at each other), then let it hang by the wire.

Then you'll have a big opening in the bottom of mirror - start from there just pry it apart(you can do it all without removing the mirror)

Then check if you have power coming to the two wires in the plug of the board(brown ground, blue - power(with ignition on)

If you do carefully inspect the board with or without removing the mirror.

In my case it was pretty evident which resistor had let go by discoloration of its ceramic coating and the board directly beneath it.

If that's your case as well carefully pry of the metal clip on the transistor which holds it the aluminum part, then unclip the board from the mirror. If you find that you don't have enough space to work with it you can desolder one of the wires going to the mirror from the board(I didn't).

Then desolder the resistor in question and once removed confirm with a multimeter that it has no continuity.

Solder the new one in I also resoldered one of the capacitor legs right next to it as it appeared to be missing solder(give the lower part of the board a good look, for any cracked joints for good measure).

Install everything in reverse order. Before installing the mirror back, compress the two pins that hold it in place so that the little piece of wire jumps between one of the pins and mirror that will make jamming it in a lot easier.

To verify that your mirror now works, cover the Photo-sensor facing the windshield and shine a light on the one facing you; you should see it dim.

Good luck.

 

Thanks. That is my next project on the car. And yes, I have the two lights and IR sensor, so your instructions will be most helpful.

 

Thanks to the clear dis-assembly instructions I was able to quickly determine that my problem was different. I do not have power to the mirror. I found the fuse blown. I disconnected the plug to the circuit board in the mirror and installed a new fuse which also blew, so I have a short somewhere. I guess a logical place for the short is in the stem of the mirror, if the insulation broke from repeated twisting of the mirror. The car has gone 220,000 miles, so the mirror has seen some adjusting. Does anyone have a wiring diagram for the mirror dimming circuit on a '97 E ?

This is the first car I have ever owned that I have not been able to buy a manufacturers shop manual for. They are permanently out of stock. Very frustrating.

 

I doubt that the insulation would brake from twisting the mirror but give it a show who knows I included the diagram for you, if you don't have dimming driver mirror simply disregard that part of the circuit, you'll be interested in the black/blue wire which brings in the power.

I imagine the plug you disconnected was at the back of the board, if so pull out the entire mirror and disconnect it from the roof wiring, also instead of burning a new fuse each time you can check it with a multi-meter or a test-light. You'll be looking for ground at the blue wire on the mirror side if it's still a ground after disconnecting the main mirror plug your short is further down the harness if not put in a new fuse and it shouldn't blow anymore - your problem is indeed in the stem.

 

Thanks for the wiring diagram. I have studied it enough to be puzzled by it. It shows the front dome light to be powered by fuse #16. The fuse is blown but the dome light works fine, dimming slowly when it turns off like I assume it should. I pulled out the dome light assembly but I could not see to the top of the mirror stem.

From your comments I gather that there should be a plug above the mirror stem connecting to the roof harness. I will try to get into this area the next chance I get. And yes, I do have the auto dimming drivers side mirror, which of course does not dim.

I am curious as to where you get your information like the wiring diagram. I noticed that it mentions the Mitchell Repair Information Co. Is this from a source I could get access to?

 

First of all you're looking in the wrong place, in order to gain access to the plug I mentioned you need to remove the mirror and not the dome lights. To do so just pull it straight down.

As for the fuses, it has been mentioned elsewhere before, and I'll repeat it again Mercedes can have different fuse configurations depending on the year and month as well as the factory they were built at. So always check your car's fuse maps to locate them and don't rely on other posts or diagrams. They will often prove accurate but not always whereas the info in your car is always spot on. Also they diagram I provided is somewhat simplified and may not be 100% accurate for your vehicle. However in this case you've misinterpreted the diagram that fuse powers the dimming function of the mirror and has nothing to do with the dome light. The rectangle in the top left refers to the mirror plug which I mentioned earlier(it isn't accessible without mirror removal).

As to your second question no unfortunately you won't be able to get access to Mitchell, I work in a body shop, so that's how I have access to it.

If you're a serious DYIer and are somewhat good with computers I would suggest that you try to locate a copy of WIS on the internet, I use an old copy which will only install on Windows XP, so to run it on 7 you'll need a Virtual Machine. That is something you can look into.

Alternatively you can purchase a subscription to ALL DATA which will give you a decent amount of info for most repairs and could also provide explanations on how things work. It's info does not cover everything that WIS covers, but the things which are covered are taken straight from WIS.

Whichever one you pick, if any will need some getting used to and figuring out how it works and where to look for what.

 

I fixed it! Someone pinched the wire bundle when the mirror was installed, between a couple metal parts. both the hot wire and the ground wire had bare spots where the insulation was worn away. I had to work up the nerve to pull hard enough to get the mirror off, and getting it reinstalled was difficult. I hope I didn't pinch any more wires as I struggled to pop it back into place. But at least it is now dimming fine, both mirrors. Thanks for the motivation and instructions CK.

 

Glad I could help.

Enjoy your mirrors

 

My auto dimming mirror part number is 2108100417, and it defective so i want to replace it.Someone has one 2108100317 and says its compatible,are they compatible?will it function 100% on my MB?
Its on a 1996/7 E230 MB,W210.