1984 300SD factory Amp location - PeachParts Mercedes-Benz Forum

qsprn · #1 08-01-2017, 07:09 PM

I apparently have a bad speaker and AMP. I have searched but no luck finding the answer. A couple people have asked this question but I didn't see any answers. Does anyone know where the original radio AMP in the 84 300sd is LOCATED. The radio works but no sound through the speakers. We hooked another speaker to the radio and it works. All the fuses check as good.
No sound from the original speakers. The cigarette lighter has stopped working as well. I have had conflicting answers, from there is no amp to look under the
rear seat or spare tire. I may have not looked hard enough.
I am mystified. Everything worked great until a couple weeks ago.
One additional piece of info. The right front window motor died and when that
was being looked at I suspect something got fried.
I do have a wiring diagram that shows the 84 and 85 have amps.
I am a little clueless about electronics. I know how to change the car's battery.
Any insight is appreciated
Thanks
Bill

Diseasel300 · #2 08-01-2017, 07:26 PM

I don't think the W126 had separate amplifiers until the very late 80s or early 90s. Most likely you have a failed fader switch in the center console by the shifter. It's a very common failure and can cause complete failure to produce sound.

qsprn · #3 08-02-2017, 06:59 AM

"I don't think the W126 had separate amplifiers until the very late 80s or early 90s. Most likely you have a failed fader switch in the center console by the shifter. It's a very common failure and can cause complete failure to produce sound."

OK Thanks. Will try that.

Diseasel300 · #4 08-02-2017, 10:32 AM

It might help to have a wiring diagram for the radio. See the attached PDF. Notice how all 4 speakers are connected to the fader switch, if it fails, no tunes.

qsprn · #5 08-03-2017, 07:13 AM

Many Thanks to Diesel300!

I also received a definitive answer on the original amp question from Beckerautosound.com. They said:

"No amp in 1984
Original radio was a cassette".

bk

qsprn · #6 08-18-2017, 08:23 AM

First, the problem is solved, but it turns out the fader control and speakers were all good.
The problem was in reality a couple of shops that did not really know what they
were doing.
The shop that put in the aftermarket radio originally broke the tabs on the center console
cover and then SILICONED the cover back on

Next, the guy who tried to trouble shoot the window motor must have
unplugged the wires to the fader and cigarette lighter somehow.
I finally found a shop that knew what they were doing. They figured it out in about twenty minutes and put everything back together included gluing the
cover tabs back on. It all works

BTW they took one look at the wires and said there is no amp in the car.
Lesson learned. Find people who know what they are doing. Not always easy.

At least I know a little more than I did before.
Thanks to Diseasel300 for pointing me in the right direction.
bill

Diseasel300 · #7 08-19-2017, 01:14 PM

Glad you got it figured out! My SDL had a failed radio in it, a failed fader, and right rear speaker blown. I think the original radio shorted out and cooked what was attached to it. In my case it was just easier to rewire the car for true 4-channel speakers and install a new head unit than it was to replace OEM and repair what was there. The factory wiring is more complicated than it should be IMHO.