Im just outside of Washington DC, in Maryland.

 

I have a c320 wagon with the same issue I took it to the dealer and they replaced the rear Sam but that didn't fix the problem. My radio auto volume never worked so after reading your thread you may have shed some light on the issue.

I would like to diagnose the problem what is the radio fuse number for my 02 c320 ? I would like to give it a shot.
Thank you for any help I can get.

 

The radio fuse is number 64, on the drivers side in the engine compartment.

The MOST ring on newer cars and the D2B ring on older cars are fiber optic coupled devices that connect audio to the loud speakers. The light pipes must carry the beam into and out of each device making a round trip from the headunit. The devices sound off when polled by the head unit, and must be connected in the order shown in the diagram. If a device is not present, the goesinta must be connected with a suitable splice to the goesouta so the loop is maintained. A car without premium audio, telephone, teleaid, satellite radio, or voice recognition has no use for the fiber optic, but should remain in a loop so the radio does not panic and cry to the front SAM he lost all his friends.

The headunit, be it COMAND or a radio, only talks to the front SAM on a copper wire high speed serial port called CANbus. The car has two cans (not a colorful South American bird) named CAN A and CAN B. CAN B connects the headunit to the front SAM. Also on the same CAN B is the instrument cluster multifunction display (MFD), the steering wheel buttons, and the steering column stalks. If a short in the data lines in the headunit occurs, it will take the bus down, and the SAM will not be able to sort bus traffic into actions.

 

WOW! that is a ton of info thank you so much for your help although some of that is Greek to me.

I did pull the radio out to have a look at the connections and it looks like the only fiber lines that are there go to the cd changer. If I replace that radio with an aftermarket one do I need to worry about the fiber lines going to the cd changer?

Also I know you can buy an installation kit with a wire harness will that be all I need to get the amp and all the speakers working?

 

Somewhat of the same thing happened to my car but far worse. I had a single din Pioneer installed last May and everything was fine until September. One day out the blue while I was driving, my car jerked and started slowing down, speedometer died, check engine light on, brake lining wear indicator on, and I'm sure I'm leaving something out. But to make a long story short, I took it to the stealership and a new relay cost me $400. All due to the connections of the single din.

 

Your car has the power amp in the headunit. It is a four channel amp. You can replace the factory headunit, but nothing will really sound better, really the tuners and amps are much the same. You might gain navigation or HD radio, but that is for you to determine. If you don't use the disc changer you can leave the fiber disconnected. Without the headunit it is of no value. If you wish to use CD's you'd look for one with an internal drive or connection to a trunk mounted unit.

A harness and mounting kit should be enough, but you really need an expert in Mercedes sound systems to not muck up the CANbus or the car power distribution system. (They don't work at Best Buy or Sammies House of Stereos)

 

Thanks for the info.
I just wanted to give an update on what I was trying to diagnosis my problem. I did remove the number 64 fuse drove the car for 8 days no issues at all. So I reinstalled the fuse and so far no problems in the last 2 days.
However one of the issues that has been happening to my radio is I will get back in my car to start it up and find the radio off this means the radio had lost power and my bass and treble all audio settings are set back to stock. But the radio stations are unchanged just the audio settings have changed. This is usally a precursor to dash light going on and off and power lose to the windows ETC.

 

Sorry to bring up an old thread but I'm having the same issues listed by OP and want to see if you guys may know the main source that is causing me issues. The current issues right now sometimes when the car is off, the high beam indicator is flashing. Once you turn the car on it takes a few seconds for the cluster to recognize that the car has been turned on. Usually when you turn on the car, the car makes the few consecutive beeps right after you turn the car over, but mine takes a few seconds after it is turned on. Now, when driving the car without the radio, the car is completely fine. Once I turn on the radio, all hell breaks loose. Everything stops working properly. Signals, wipers, ac stops blowing air but the compressor stays on, windows, all the button functions on the dash, fuel needle, cluster and buttons on the dash that are illuminated go dark. Before when driving with the radio on, I would have these issues for a few seconds then everything would go back to normal. Now, once you turn the radio on, a few seconds after everything stops working and they will not work until the radio is turned off and sometimes I would have to turn off and turn the car back on for the functions to start working again. I know I should really bring the car to a shop, but I happened to bring the car to a shop about two weeks ago to go under "diagnostics" and they said they couldn't source out the issue because the car didn't "act up" while it was there. This was a shop that said they specialize in Mercedes and BMW, but from the amount of E39's and E46's I saw over there, I'm kind of questioning their knowledge on Mercedes.. I was actually going to bring the car to a shop tomorrow, but for some odd reason the ignition isn't reading the key now.. I'm not sure if that has to do anything that's been happening and could just had happened at a really inconvenient time.. I don't have a second key and will be going to a dealer today to get a second one.. So now I can't bring the car to the shop which is why I'm here. I wanted to find out if you guys would happen to know what the main culprit would be.. from what I've read through this thread, I'm pretty sure the Head unit is the main culprit and causing issues to the D2b.
So if you could enlighten me on what the main issue is, that would be super awesome! Thanks in advance guys.

 

I have read a few threads of this happening to people. They solved the problem by replacing either the stock head unit or the CD changer. However taking out the radio fuse seems to always be a sure-fire temporary fix when the radio is the issue.

I had a similar problem but the only symptoms I had was that the instrument cluster died and my headlights would not turn off. I had an aftermarket head unit installed at a shop, but everything was fine after that. My problem started when I removed the factory CD changer.

I took my car to an independent and they reset the ECU (they told me the BUS got tripped). Problem solved, never returned.

I have also read of others having similar problems where in a couple cases it was a dying battery and on a couple other occasions a bad headlight switch.

Just throwing this out to give an idea of the wide variety of issues that can be the source.

 

Always make sure the front fuse box cover is fitted correctly. All these issues relate to front SAM problems. If any water gets onto that fuse box you can sure it will make the dash light up like a xmas tree.

 

It will not turn. Drove it earlier within the morning and it was totally fine. Had to go in for a meeting and it would not turn. I am suspecting that it is the key.. I am not exactly sure. Usually when the EIS recognizes the key, it will make the buzz noise, it doesn't do that at all now. I'd rather get a new key now just to make sure that it is the key and hopefully not the EIS that will cost quite a lot. To recall, my car had a hard time starting up a few times when cold recently. Maybe it's the battery and it's not giving enough voltage to the EIS? But my lights and everything else works fine.. Sorry to hijack this thread with another issue.. On to the main problem.

Edit - Just checked the car, turned on the lights and they started to flicker.. Dome light and reading lights don't turn on. Maybe it's just the battery? or I can just start a new thread lol. Sorry guys!

When the radio is turned on, that's when all the issues seem to happen. If the radio is off and never turned on, the car is fine. I'm assuming it is the radio, but maybe the BUS could have gotten tripped and the ECU just needs a reset just like what happen with you. The CD changer went out a while ago. I would say it's been about 2-3 years since I've had it. It just stopped working one day. Wouldn't recognize that the CD changer was there so I just started using an AUX/Cassette adapter. I would like to bring it to the shop you recommend to me, Euro but I can't do that now with the whole key situation sadly..

 

I would replace the key.

 

Battery went bad lol. Everything's fine now aside from the d2b issue.

 

Sir I need urgent assistance.
My car battery runs down whenever I used AC the following morning it will not start till I bring another battery to start it.
I've changed the alternator yet it continues.
I ve changed battery yet it continues. Sometimes it will write Battery/Alternator visit workshop.
Am tired don't no what to do.
The car is C320 (203).

 

So if you don't use the AC the next day the car is fine?

 

That's very weird that using AC will kill battery. I would check the charge rate at the battery with AC on and with additional loads. Blower fan lights the lot. If that passes. Check for battery drain. Hopefully your new battery is good! But if you getting visit workshop on your display you going to find a fault in your charging system