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1988 MB 300SEL
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Discussion Starter #1 (Edited)
I finally got my 300SEL running & now I'm installing a decent radio in it. (Blaupunkt Hamburg) That way I can connect my Sirius and MP3 player and rock out. The only problem is, I got the car with no radio & the wires are cut at the harness. I've got batt, switched pwr & grd hooked up but the speaker wires are a mystery to me. Nothing at all on Mitchel On LIne (worthless for this, no info whatsoever). Also, I need to bypass the fader control on the console so I can use the radio's controls. Does anyone have or know where I can get a wiring diagram for this circuit? HELP! I don't want to have to gut the car to run all new wires. Thanks,Vince
 

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1996 c220
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11 Posts
go to best buy get a wiring harness hook it up yourself comes with direction.
this is what i did for an after market radio and works perfect. cost me 30.00 us
 

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1988 MB 300SEL
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40 Posts
Discussion Starter #3
I got the unit from Crutchfield with the harness that hooks to the MB factory harness, same as Best Buy or Radio Shack makes. My problem is that the MB harness plugs have been cut off. I have a bunch of wires of various colors that I don't know where they go. I even pulled the console up and checked the fader wiring to see it would help me out. No help. If I knew what color wires went to what speakers, I could have it hooked up in 5 min. That's why I need a schematic. Thanks anyway.
 

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1993 300TE, 1995 E320 Wagon
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1,895 Posts
Vince-

My PO had replaced the original Becker at one time, and wrote down some notes when rewiring. I have the 560 SEL with the "10-speaker" setup, but I'm fairly sure that MB would have used the same wiring colors throughout the line. There may be exceptions, of course. I would think you could check continuity on wire pairs with a multimeter, and if you use this list, it'll probably shorten the process. I'm currently trying figure out how to scan in the original MB wiring diagrams I have, and I'll post them later if I'm successful.

Here's the list:

RF and LF (neg) - grey
RF and LF (pos) - grey/black
RF and LR (neg) - black
RF and LR (pos) - yellow/black
Ground - brown.

The original diagrams have the following (coming out of the radio):

signal ground - white to the left amp, and yellow to the right amp
Left sound system output - blue
Right sound system output - red
Cable shield ground - brown

Good luck!

Dave
 

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1993 300TE, 1995 E320 Wagon
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Here's the scan(s) of the wiring diagrams. I hope that you can read them...

D
 

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1988 MB 300SEL
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40 Posts
Discussion Starter #6
Wow, thanks. These should help a lot. I'm ending up today's session, but I'm going to look at the car in the AM. Thanks again,Vince
 

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1991 300SEL
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212 Posts
Wow, thanks. These should help a lot. I'm ending up today's session, but I'm going to look at the car in the AM. Thanks again,Vince
Hopefully you don't end up with the issue I have, Certain things disrupt the sound to the radio, so it's either open the door, press the window buttons or turn on the interior light to get the sound back. It's an issue with the antenna connection, not sure what to do about it.

The issue with my wiring turned out to be an issue with the amps, So I was forced to wire the HU directly to the speakers. Sounds great though, Factory speakers aren't bad at all (in my case atleast, just make sure you have your polarities right).
 

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2004 S500 4Matic, 2018 Ford Expedition Max, 2017 Jaguar F-Pace S, 2016 BMW 750i
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I too am in the process of installing a Blaupunkt head unit, the MP47. The car came with a Blaupunkt Tokyo that was riding off into the sunset. I anticipated an easy swap, however, the wiring by the installer was poorly done and I have been studying the wiring diagrams to make sense of it all.

Come to find out, the installer tapped into the red and blue Becker wires with only the RR channel, amplified no less. Thank goodness the Becker amps were not fried-they seem OK.

If you are keeping the wiring harness intact and running the signal through the Becker amps, use the preamp out wires (it comes with your unit, yellow block with RCA plugs). Cut off the RCA plugs to the front Right and front Left and splice them into the red Becker wire and blue wire, respectively.

This will allow you to enjoy music for a while and get energy to pull new wire to new speakers. Believe it or not, though, the Becker speakers sound rather decent with an upgraded HU. Best wishes
 

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1988 MB 300SEL
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40 Posts
Discussion Starter #9
Actually, I,m not 100% sure I have the system with the amps. I spent most of the day getting the engine to run right. From everything I've heard on the forum, the original system isn't very reliable. I'm probably just going to have to bite the bullet & run all new wiring. Probably use a very strong pioneer amp I have and use the front door speakers as subwoffers, wire crossovers into the dash speakers and run straight to the rears using another amp. Should be enough to make my ears bleed. 1 more thing, can anyone tell me how to remove the grills from the rear spkrs? There is a secret screw or fastener that I can find. Any help would be appreciated. Thanks,Vince
 

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1990 SEC
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4,245 Posts
1 more thing, can anyone tell me how to remove the grills from the rear spkrs? There is a secret screw or fastener that I can find. Any help would be appreciated. Thanks,Vince
No fasteners I'm afraid. You need to remove the seatback and then pull the speaker covers straight (horizontally) forward.

Be very careful. The plastic has probably gotten brittle from baking in the sun all those years and if you break one of the tabs, a replacement cover will be hard to find.
 

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1989 300 SEL "Heidi" will this be the most expensive $1000.00 car I've ever owned?
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1989 300 SEL (others?) Recommendation...if you are going to bypas the factory amps...you can still use the factory wiring....intercept all the speaker wiring behind the rear seat at the twin amplifiers Then run speaker wires straight up to your head unit. I used a 9 conductor cable to accomplish this, because I'm not putting a high wattage receiver in. This works of course if you are going to use the factory speakers. Even if you are going to change out most speakers, easier to use most of their wiring. Be mindful of wattage...most 80's 90's stereo unit didnt put out huge amounts of power.If you are amping up to hundreds of watts, use a heavier cable.

factory Door locations appear to me to be a woofer/midrange speaker in the door and crossovered with high pass filter to the dash tweeter speakers (4 inch on a 300SEL). You might have to fiddle with that end of the wiring if doing something different.
 

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1989 300 SEL "Heidi" will this be the most expensive $1000.00 car I've ever owned?
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these threads are just as useful to me as if they were written yesterday...as I work through this auto, i search and find...and have found solutions from 10 year old threads ...I hope i give someone else an idea
 

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Just messing with you, dberry.

Here are some diagrams in case anyone else is interested.


..





 

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1986/1990 W126
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Axelwulfs car. He doesn't seem to come on any more.
 

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Axelwulfs car. He doesn't seem to come on any more.

Yes, I found his Photobucket.

Last couple of posts in that thread was about the SEC being vandalized at a shop where it was getting major engine work.

A shame.
 

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1991 560 SEC 1994 E500 2014 E350 Cab
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Could be a Wooky someday!
 

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1991 560 SEC 1994 E500 2014 E350 Cab
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7,028 Posts
The 500E is an amazing car. Been searching for the right one myself.
 

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'91 560SEC, '91 300SE (sold), '98 Yota, '02 S-10 Hauler
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