kenvaux

I purchased this 2000 ml 430 about 4 months ago and now the MCS has no audio. It died with a popping noise, came back on then later several pops and then nothing. All the lights are on, display functions, cd changer operates but just no audio except for a very slight hiss. I have a wiring diagram for the system but audio and control lines are not identified. I want to check for audio signals from the head to the amp to isolate the problem to either unit. Anyone able to tell me the color codes for the audio wires to the amp ? Thanks, Ken

smo0othride

This is something I copied from another post, maybe it will help:
(I also have a full Bose system (MCS, speakers, sub) for sale that was pulled from my ml500)

Harness with 15 wires.
Signal from Head unit. (thinner gauge wires) (Bank B)
b8 Red & b10 gray = Right rear signal
b5 Blue & b12 green = Left Front signal
b6 Orange & b9 White = Right Front signal
b7 Pink & b11 Orange = Left Rear signal

To Speaker. (These are slightly thicker gauge wires) (Bank A)
a8 Orange & a7 White = Rear Front speaker
a12 Blue & a11 Green = Left Front speaker
a9 Red & a10 Gray = Right Rear speaker

harness with 8 wires
Pink & Orange wire = Left Rear speaker

If you map it out basically you match the color on the 15 wire harness. You will get one Orange wire left over that is not group together with the signal and speaker wires.

You have to match Pink & Orange with the 15 wire harness to the Pink and Orange on the 8 wire harness for the Left rear speaker. I found it odd they didn't put it to the same harness.

kenvaux

Thanks for the info.... I tracked the problem down to the head unit. I noticed that when scanning for a station the scan would not stop. I felt from that the scan looks at the audio output to give it an indication of the presence of a station which told me that the problem was in the audio output section of the head unit. Not having any radio removal keys I found a article on youtube that described making a set of keys from a old credit card. they worked great.

I removed the head unit and and after a bit of troubleshooting discovered that by smacking the head unit on its side with my hand it would start to work for a short period indicating a bad connection in the audio amp section or a poor solder joint/cracked circuit board. I disassembled the head unit and removed the audio amp section located at the rear of the unit. The audio amp connects to the main board through two multi-pin sockets and a plugin harness. I cleaned all with a electronic contact cleaner, reassembled and installed the head unit and it is working fine.
This was not a difficult job but you must go slow and photograph each stage of disassembly.