I have the exact same issue. I've done a lot of searches and you'll be farther ahead by going over to Benzworld.org. One suggestion was that the cause of the low or non audible volume on the FM is due to a faulty microphone that is housed in the rear view mirror base housing that is affixed to the windshield. On BW they posted up some MB diagrams and fix instructions, but it is extremely involved: must take apart the overhead console to get to the RV mirror so you can remove a certain clip to remove the mirror housing THEN find the little microphone to disconnect....and so forth.
I got a set of plastic pry tools to attack the overhead console, but I have yet to correspond with anyone who has actually DONE this operation. Most people elect to replace the entire head unit with an aftermarket unit like a Pioneer, which offers all the new features and none of the headaches of the stock MB head unit. VERY tempting I must admit.
I have hesitated to go after the speed-dependent volume microphone on my ML for fear of breaking other things and the possibility that the proposed fix won't work.
If anyone on this forum has successfully disconnected the microphone that affects the FM volume on an ML of the 03-04 vintage, I'd love to get the details. THANKS.
I just went to EPC to look at the parts diagrams. From what I see, the rear view mirror & housing is a separate assembly from the overhead controls housing. You should not have to remove the controls housing to get the cover for the rear view mirror cover (where the microphone and rain sensor are) from the way it looks. Diagrams can be deceiving, though.
I've re-read everything and I think I may know how to remove the housing for the microphone. I'm going to try it today and I will post results tonight or tomorrow.
Cross your fingers. It should not be this hard...but then again...we are dealing with MB over-engineering.
Thank you very much for your help in trying to resolve this problem. I was able to get my RV mirror off. It fits on a U shape housing.I got it off by pulling down on the mirror stalk and pulling it out from the bottom at the same time (be careful). There is a box attached to the windshield with 2 wires plugged into it. One wire goes up under the headliner into the console. The other wire plugs into the plasyc mirror housing. The wire covering was dried out and frayed wires where sticking through it.I have a few pictures off it but i dont know how to post them with this reply. But going togive it a try. By the way what is EPC?
Which way did you pull? Down and towards the front of the car, the rear?? I'd love to see a photo. So you did not have to remove anything else? BTW, does the FM volume work now? Funny...I was trying to help and now it's me that has all the questions.
EPC net is a Mercedes Benz online service that allows you to look up any part for any Benz. Every assembly has diagrams. You have to register and even provide a credit card #, even though it's free...unless you want to access European models.
I pull down and towards me also with a twisting left and right Because the attaching piece is a U shaped metal piece on the winshield. Now that frees the mirror housing. My RV is not auto dimming.But there is fitting inside the housing and runs to a connection to the box attached to the mirrorme is still low because this just the beginning of the problem. Finally got pics up
Thanks for putting up the photos. I don't see the microphone that the diagrams showed. I wonder if the FM volume problem is with the amplifier.
One other strange thing that happened when I had FM volume and still happens with the CD volume is that when I drive near high power electrical lines, the volume ramps up to near max without touching the controls. When I turn away, the volume drops back down. THAT is a mystery.
Well....cracked the damn windshield trying to get the mirror off. That does it. I may look at disconnecting the microphone when the windshield gets replaced, but now the project has an extra $250 cost in the form of the insurance deductible. I could have put that towards a new head unit. Warning - it did not take much force at all to crack the windshield.
First an apology - I neglected to report back on the solution to my particular situation. After all the reading, probing, breaking and swearing, I finally sent my head unit off to Becker Autosound after talking with them about what all had happened. It came back expertly rebuilt and has worked flawlessly ever since. That was almost two years ago.
I would recommend doing this. ALL the symptoms could be traced back to a defective head unit. Eventually, everything will go: AM volume, CD player volume...everything.