The PO replaced the head unit on my '81 300TD. The console fader was working when I got the car so I decided to bypass the fader along with replacing the stock speakers. I replaced all 4 speakers with inexpensive coaxial Pioneers.
I snipped the wires going to and from the fader under the shift surround but now I have the shift surround apart and cannot get my rear speakers to do more than a whisper when the fronts are really pouring out great sound.
I've got one large wiring harness coming from under the ashtray which contains 2 red/black, 2 green/black, and 4 plain black (which were originally spliced together in 2 pairs).
Then I've got a smaller harness which is coming up from just to the right of the shifter which has one green/black, one red/black, and two single plain black (I'm pretty sure that these are the rear ones, right?)
I can get the front ones sounding great but the back ones are so quiet they are nonexistent.
If only I had a wiring diagram!