Hey guys, some assistance please. I feel a little stupid. The Becker Grand Prix head unit in the referenced vehicle is trash, so I'm installing a single-CD replacement head unit (a Blaupunkt CD unit I've had lying around for awhile). I've searched the archives, but I haven't been able to find any description of the wiring that remotely resembles my car. The speaker connections, antenna power lead (blue wire) and antenna connection are obvious. What isn't obvious are the power connections. Some help here would be appreciated.

There are two wires bundled together which go into a two-pin connector which then leads to the the four-pin connector on the back of the Becker. One wire is red (I think this is a constant on and I'm using it so) the other is grey (I think this is a ground). There is a single black wire, of a slightly larger gauge than the red and grey wires (which I believe is a key-on lead but which doesn't act like it) which also feeds into the four-pin connector. The four-pin also contains a very short brown wire which is connected to the ground terminal on the back of the Becker. There are also two other wires - a brown/green which goes to a connection on the back of the unit and a brown/green (slightly lighter green color) which was grounded to the terminal on the back of the Becker. (I have no clue as to what those last two wires are all about but sort of guessed that they had to do with the alarm system.)

Is the black wire the key-on lead (see below)?

Here's what makes me feel stupid. I've done radio-to-CD conversions on 3 Benzes (all older than my 300E), one BMW, one Audi, a Honda and two Toyotas. None of them had alarms integral to the radio. The 300E has be baffled. Because some of that wiring back there must be related to the alarm, I'm worried that I'm going to short something out and create a nasty little instrument cluster fire. Here's why.

The black wire which I thought was the key-on lead acts strangely. It powers up when the driver's side door is opened AND when the key goes to position 1 or 2. Thus, if I were to use it as the key-on lead and didn't want the radio coming on every time I turned off the car and got out, I'd have to make sure that the CD/radio is switched off every time I open the driver's side door.

That can't be correct.

Help.

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David
1986 300E - "Liesl"
(107K)
1978 300D - "Gunther"
(147K)

[This message has been edited by dtanesq (edited 11-16-2000).]

Hello: I figure you probably figured this out by now, but I did just this very thing a few nights ago. I found on my becker radio, there is a plug with 4 wires, and the plug itself is numbered 1-4.

1 is BR and goes to ground
2 is sw/ge and is the acc position
3 is gr/vi and is hooked up to the park/headlight circuit for backlighting if your receiver is so equipped.
4 is rt and is 12v all the time.

I had another plug, with places for 5 terminals, but only one wire, brown went to this plug. I had no idea where this went, and my Nakamichi cd45z performs flawlessly without it. I merely taped it up. You said you had figured out how the speakers go, so I won't go into any of that. If I can halp in any way further, let me know.

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Ron Miller
1986 300E

Ron:

Thanks for your reply. I have the following question. What did you mean, for the acc position wire - sw/ge ?

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David
1986 300E - "Liesl"
(107K)
1978 300D - "Gunther"
(147K)

According to my wiring diagram, taken from a manual titled Mercedes W124 1985 to 1995, published by Technibooks, and is called an owners workshop manual, sw=black, and ge =yellow. here are the colors listed in the manual...

bl=blue
br=brown
el=ivory
ge=yellow
gn=green
gr=gray
nf=natural
rs=pink
rt=red
sw=black
vi=violet
ws=white


As far as the circuits go, I measured the terminals on the plug going to the radio using a Fluke digital vom. My Nak works fine, although I have absolutely no idea what the other plug with one wire I described earlier does. Mine was a single plug that had 1-5 numbered on the plug, and had a brown wire with a blue tracer on it. Hope some of this helps.

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Ron Miller
1986 300E

Ron:

How do you like the Nak45z? I am looking at putting one in my 87300E, with DiamondAudio speakers. (Just as soon as I recover from having to stuff a new engine in my POS Acura Legend 5 spd) . The Nak looks the cleanest of any of the aftermarket units out there - I really don't want a juke box or diving dolphins in my dash. I am curious how it sounds. Thanks for any info.

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JCE
87 300E, 65k miles
Smoke Silver

This is what you want to do, go out and get a test light. inexpensive. Ground the wire on the test light, and use it to touch the wires. you need 3 main wires for the radio

12 Volt constant for radio station memory.

ACC/key on power for providing power to the radio when the key is on and turns off the radio when the key is int he off postion.

Ground - this needs to be attached to the metal of the car. an easy way to test for ground is to hook the test light up to the constant power wire and check for the ground.

After that, antenna, antenna power lead, and speakers, and you are set to go.

Easiest way to test the speakers is to use a battery, generally a 1.5 volt batter isnt enough as I have found but some say you can use it I just havent had luck with them myself. I use a drill battery, but a 9 volt battery will work fine too.

Alon

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'92 300CE
Metallic Black (Blue Flaked) on Parchment
Clear Corners
94-95 Tail-Lights
Debadged
Black Grille Insert
78.5k Miles

Future Upgrades:
Sportline Suspension
17" AMG Monoblocks or EVO II's
Euro Headlights
Performance Chip
AMG Exhaust

Click here to Go To My 300CE Page

JCE

So far the Nak is working fine, and sounds great. I did not even compare it with any other player, because where I live, there is simply no where to go demo one less that 3 hours drive from me. I read some other forums, namely sounddomain dot com, and looked at what all the current rage is. I'm a little over 40, so gut thumping bass is not any of my desires. The Nak unit is very clean looking, simple to operate, and has the features I need. As you prob know, it is not lit up like a major city and does not have a faceplate full of buttons. I'm very happy so far.

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Ron Miller
1986 300E

Thank you all.

As far as the colors, I should've remembered these cars are German. Interestingly enough, Ashman's reply is going to be the most helpful because the wiring in my car is different from yours, Ron. There is no sw/ge wire in the system and no br ground wire. While some of you were writing replies, I was out buying a circuit tester.

One caution for anyone else reading this string. Ashman wrote that you can test for ground simply by wiring up the circuit tester to the constant on lead and poking around for a ground. In my car there is a black wire which is part of the instrument cluster/right rear tail light circuit which will ACT like a ground when the key is off, but which, when the key goes to the 1 or 2 position or the driver's door is opened, will power up and blow the #9 fuse.

Thanks again, all. By the way, I, like Ron, am a little over 40, but feel that my Blaupunkt CD147 application needs more bass. Full symphonic music, in fact, all music (I am a classical musician) loses something if the low bass isn't present. Having the full spectrum of sound present makes any genre of music more exciting to listen to - from Bach to Warren Zevon (with my wife's Radiohead in between...). The full spectrum problem is intriguing enough in home stereo, as you all are probably aware. We spend plenty on highly engineered components for our home systems. Car stereo is somewhat complicated, because road and wind noises, and vehicle noises (whether audible or not) interfere with and degrade stereo output. I think to begin, the speakers in my car will be replaced, then some thought will be given to a subwoofer setup.

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David
1986 300E - "Liesl"
(107K)
1978 300D - "Gunther"
(147K)

Glad to be of assistance. I just happen to have a nice digital vom in my toolbox. I used to work on some electronics years ago, and I just like to have a good meter. You are right on the different cars having diff wiring diagrams and circuits, the info I gave was for mine. I traced the schematic to see where the wires went, and also measured them just to make sure I did it right. I shaved some insulation off near the plug on mine so that if I ever wanted to put the factory radio back in, it will be a simple job. I was curious if the plug on your car was the same as mine... the four wire plug going to the becker? I had to look hard, but they are numbered 1,2,3,and 4 right by the terminals.

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Ron Miller
1986 300E

[This message has been edited by Ron Miller (edited 11-18-2000).]

In Mercedes The Brown lead is ground. Brown standing for Negative Earth.

I did say you can ground it by attaching the ground to some metal. which is the easiest way to do it.

It is always a good idea to test with ignition on and off, some things will change polarity like you said when key is on or off.

I myself use a multimeter and test for voltage, test lights are simple and cheap and work similar.

I myself have never blown a fuse installing a radio, though I did once hook up the ground to the illumination wire and fired a radio. This was of course the first and only time it happened.

Alon

------------------
'92 300CE
Metallic Black (Blue Flaked) on Parchment
Clear Corners
94-95 Tail-Lights
Debadged
Black Grille Insert
78.5k Miles

Future Upgrades:
Sportline Suspension
17" AMG Monoblocks or EVO II's
Euro Headlights
Performance Chip
AMG Exhaust

Click here to Go To My 300CE Page