Qbee1995

I brought my car in for service after receiving a "visit workshop" message due to low voltage. They changed out the batteries and did the regular service, air conditioning charge, and replaced a light bulb. Now my radio, CD player, & navigation system is not working. When turned on, the MB logo appears for about 5 seconds, then goes off. They did not use an alternative power source while changing the batteries (I asked), so the car was completely dead. The service technician ticked me off because he didn't even want to talk to me about it, and basically said I need a new Comand unit- at the cost of $1780...they are an authorized MB service center, and I've never had problems before, but I'm very suspicious because everything was working perfectly when I brought my car in. The fact that he didn't even want to talk to me about what was done added to that.

Does anyone have any suggestions on how to get the unit working? Or is it possible they fried it?

Thanks in advance!

konigstiger

Disconnect main battery (trunk) for 5 minutes or so. If this does not clear it since it is an authorized MB shop, repair is covered for 12 months/unlimited mileage have them revisit using MB DAS to check for fault code(s) - may be as simple as blown fuse for device on MOST loop.

bbspoolside

Check the fuse in the trunk by the spare wheel

Qbee1995

Thank you very much for the responses! Brought it back to the shop without success. They disconnected the battery and checked all fuses, saying none were blown. They do not have the computer to check the MOST loop, so I'm stuck. I live about 80 miles from the nearest dealership and I'm certain that trip is going to cost a lot more than the gas to get there.

The unit turns on, displays the MB logo on the screen for approximately 30 seconds now, but then goes off. The CD player in the trunk with the navi disc is blinking continuously. Now my seats/steering column don't respond to the smart key (do not go into position and then go back/up when key removed) and won't program, either. When I go to the settings menu to try and turn on the convenience function for the seat & steering wheel, it says "off" and will not allow me to change the selection. I don't know if that has anything to do with what's going on with the Harmon- Kardon/Comand system or not.

Does anyone have any other suggestions? All will be greatly appreciated!

Honcho

You'll need to buy a MOST bypass loop:

Qbee1995

After watching the video, I'm certain that is the issue and know how to fix it! I can't tell you how grateful I am! Will be on my way to the shop this morning to give said "technician" a tutorial. Maybe he can take it from there...

Thanks again! You guys are the best!

Qbee1995

After searching the internet for days looking for a bypass loop like the one shown in the video, I FINALLY found a part number and wanted to share with anyone looking for this thing. It is a "Mercedes Benz specialty tool" and the part number is 900-589-19-21-00. It is called an Optical Short Circuit Plug. I ordered it from my MB dealership and will have it in hand next Tuesday along with the Fiber Optic Bypass Coupler - Part number 000-545-33-84 to bypass the non-functioning component in the MOST loop. Hope this will help save someone else a little time. The plug costs $21 & the coupler $7 at the dealership.

Thanks again to all for their help! Hopefully, I will have music again early next week!

Stuttgarten

Excellent video, thanks Honcho!

Qbee1995

First of all, I'd like to thank those people who replied and assisted with this problem. I realized I never posted a follow up, so here goes:

We ordered the Optical Loop Bypass Tool from the MB Special Tools section, and systematically went through each component, bypassing and checking. The component that was the problem for me was the 7 disc cd changer - of course the last component on the list! We connected the bypass tool to the cd changer's fiber optic plug and voila! I had my radio, navigation, and other components working again! Once the faulty component was identified, we attached the loop coupler, permanently bypassing the cd changer ( or at least until I can find one that works to swap it out ).

This cost us about 2 hours of our time, following the instructions from the video (another post in this thread), $21 for the bypass tool, + $7 for the loop coupler, instead of God only knows how much at the MB dealership.

Thanks again to all, and hopefully this will help someone else experiencing this issue down the road!

starbrite

Thanks for the update.....good info!

ps2cho

Just wanted to say THANK YOU for the part's #'s and info in this thread. You saved me probably hundreds from the dealer. My headunit would turn on, freeze and shut off. I ID'd the bad module and used the coupler to bypass it. System booted right up!!! Found the problem!

BGS273

Thanks HONCHO for the great video! I have been having an intermittant pop where the audio cuts out for a few seconds and then comes back on. You have likely saved me hundreds of dollars for a new tele-aid module. AWESOME!

Honcho

Thank you kindly for the credit of finding and posting it, but to HiTechElectronic who produced the video.

S430LUCKDRAGON

Does any one know where the second video is located to show me exactly how to take the command unit out and remove the disc changer ? Also can I assume that the 2 special tools will work on other MB models ?

S430LUCKDRAGON

Can some one please help me ? My E 500 has the stereo / head unit problem
I called my local mercedes dealer and gave them the part numbers in this thread and here is what i got ! When i took the electrical wiring apart on the Navi Cd changer and other modules the female side of the loop that they sold me was too small for the the male ends of the Stereo equiptment wiring they were saying something about me having to take this tool apart but i didnt fall for after reading this thread , does any one know where i can order the right fiber optic loop from ? Or should i keep the one that they sold me and take it apart ? Would this work ? Thanks in adavance !!!!

RCPDesigns

Can you post pictures of both? Let's see the connector that goes into the CD changer. If it is bigger than the loop you have, I think your fibre system is actually D2B and not MOST... in which case you need a different part and/or take everything apart and try to make it work.

S430LUCKDRAGON

I took it apart and it doesnt fit any of the wiring harnesses any where , but i kbow a guy who is a beast with mercedes and he said skip all that and replace the disc changer so i ordered one i hope he was right lol

BenzDriverrr

Here's a simple DB2 bypass loop to safely remove your CD changer : D2B Fiber Optic Bypass Loop Compatible with Mercedes 1998-2003