High everyone I'm a new member from Perth Australia
My daughter has been playing music in the car via blue tooth using media player for the past 3 years with problem. But when her phone rang she would have to talk on the phone manually. My wife noticed this and changed the settings in the head unit to phone setup so she could play music and talk on the phone using the car system. Tested it and worked fine for music and phone.
Next morning my daughter, could not get any sound from the speakers on any function, not even am/fm radio. My wife set it back to media, reset system, I looked on line and found out , that to reset the system properly you need to find the fuse to the audio system, remove them for 3 minutes. Didn't work. I unplugged the fiber optic cable from the amp and noticed 1 of the connectors on the amp will stay illuminated red for approx 5 seconds and then flash, but the connectors in the cable connector do not light up at all.
Does anyone have any idea what the problem could be or does anyone know where I could find a fault finding procedure or even a wiring diagram. Any help would be much appreciated.

You can try to restart the Radio keeping the On button pressed till a strange noise appears. Also if still the optical is out, you can check if during power Off to On or during restart of the Radio the red signal light can be seen on the cable side - from Radio to amp.

moved to W246 forum...

Thank you for your advice trigital. I tried holding the horn button but get no sound, could be because I get no sound at all from speakers. I do get a red light at one of the pins in the cable that plugs in to the amp when the system starts, it stays on for 5 seconds, then it flashes for 5 seconds then it goes out and stays out. I've since learnt how to access the engineering screen by holding 1 , # and red phone button at the same time. I have fault codes DTCd018 Ring Break Pos. 1, plus ch1,2,3 and 4 Loudspeaker open. I did reset the system. But still no sound.

I've been watching people on the computer testing components in the optical loop, they are using an optical plug in bypass loop to isolate each component e.g. telephone, sat nav and multimedia. I do realize I can not bypass the head unit and the amp. But if you know how to locate the other components that would be really helpful.
Thanks for your help
Dave

What about the test from #2? Each component ( you can get the list of components from VIN ) has to receive and send optical, so you can test.... with your eyes...

Hi mate
I'm a bit unsure what you mean by "the test from #2?". Also, not srue where to enter my VIN to get a list of component and their locations?
Cheers

Dave

Hi trigital
Sorry just noticed the #2 at top right. But can't get any sound when I hold the ON button in for a couple of minutes and yes I have red light at the cable end during start up.

Hi, Thanks for your help on this. I ended up taking the car to a Mercedes specialist, and within minutes their diagnostic equipment identified the amp had a fault. A new replacement is Au$3000. Took a chance and purchased a used amp on eBay for Au $270 including freight. Works fine.