I was reading some of the W126 posts with interest as I'm trying to decide what to do with my stereo system. Maintaining the Becker provenance will cost more than I feel is reasonable, but I'm not looking for audio quality much better than the Becker provides.

I had the impression that the head unit outputs went through the fader, then to the amps. But someone stated that the head unit output went through the amps, then to the fader. Kind of a long trip, but what do I know.

Can someone please verify that my impression is wrong and that the signal goes through the amplifier first and the fader next?

This will help me decide where to tap into the factory harness to get to the speakers.

On the topic of speakers, is the overall impedance of the front speakers (dash and doors) 4 ohms? For that matter, is the impedance of the rear deck speakers 4 ohms?

Thanks,
Sixto
91 300SE

Your radio connect to the fader, and from the fader to the speakers or additional amplifier.

Actually what you heard is correct. The Becker unit works as a two piece head/pre-amp/control unit, so your in-dash system is a cassette player, an input device (selecting bass/treble, etc.) and the actual brains of the system are in the second module in the trunk. The signal then goes from the 2nd module to the amps (the two amps are divided by left/right, not front/back), then all 4 channels go up to the fader in between the front seats then back out to the speakers.
I have the W124 ETM (Electrical Troubleshooting Manual, W124 1986-1992) and it has the diagrams. Your '91 W126 uses the same radio.

I understand the wire routing from this thread, I think.... So I can bypass the fader at the fader and not have to tear the whole car apart looking for other connections ? Here is the problem I'm having; Premium Sound System with no sound from the driver door and intermittant (not very often) sound from L/R speaker, both fronts work good, right door and R/R good. I was thinking that this might be a fader problem.

Next, if a fader problem can I just use jumper wires in the disconnected plug and tape them in place ?

Thanks to any replies.

__________________
1991 300SE (my ride, 279,000 miles, looks almost new
1954 Cadillac (21 yo son's car, he bought when age 15)
1972 SeaBird 19 ft runabout (old but solid, slant six, Volvo sterndrive perfect condition, undergoing complete overhaul and refit)
1998 Toyota Rav4 (my sons daily driver when he is in the Continental US, PROUDLY serving in US Navy)

The system is configured like this The pre-amp signal comes out of the tuner module in the trunk and goes two channel to the fader control and 4 ch out of the fader control then to the amps. Here is a pic of the diagram. #1 when putting a new stereo in you also have to run an antenna coaxial cable from the dash to the tuner module in the trunk. Good Luck!

Scott@lajollaaudio

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The Mercedes Specialists Since 1986

No diagram pic came through on your reply SCLJA. So, what you are saying is I might have a problem from the amps since I do have sound from the R/F speaker, are the amps under/behind the seat. I checked the unitover the R/R wheel in the boot and everything seems to be plugged in and tight.

Thanks again.

__________________
1991 300SE (my ride, 279,000 miles, looks almost new
1954 Cadillac (21 yo son's car, he bought when age 15)
1972 SeaBird 19 ft runabout (old but solid, slant six, Volvo sterndrive perfect condition, undergoing complete overhaul and refit)
1998 Toyota Rav4 (my sons daily driver when he is in the Continental US, PROUDLY serving in US Navy)

Bruce,

The dash and door speakers are wired in parallel so if you're getting sound from the left dash speaker, the fader isn't the problem. Nor, for that matter is the left amp.

My guess is that something's not right with the left amp and maybe you only perceive good sound from the left dash speaker.

The amps are behind the seat back and cover the holes that allow access to the upper shock mounts.

Sixto
91 300SE
87 300SDL
83 300SD

.....here's what I did last night, took the seat out and swapped the amps, one side to the other. This seemed to help somewhat (got decent sound from L/R speaker) but today I noticed the same problem and still nothing from the driver door at all. There has been a few times recently that the system seemed to work correctly and then suddenly L/R dropped out. I' starting to suspect a bad speaker but hesitate due to the fact that when it does work at all it works fantastic. No pinched wires have been located so far. Is the speaker bolted in or with plastic tabs ?

Thanks

__________________
1991 300SE (my ride, 279,000 miles, looks almost new
1954 Cadillac (21 yo son's car, he bought when age 15)
1972 SeaBird 19 ft runabout (old but solid, slant six, Volvo sterndrive perfect condition, undergoing complete overhaul and refit)
1998 Toyota Rav4 (my sons daily driver when he is in the Continental US, PROUDLY serving in US Navy)