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).]