Brian,
What a mess! Sounds similar to others I have seen.
Depending on the radio you use, and the condition of your current wiring,
you may be in for a bit of wiring. Hopefully, others will respond as well,
and we can compare notes.
The original Becker has two audio or speaker outputs: a left and a right.
The fader control located in the console divides these outputs between the
front and back. If you use an aftermarket radio, it is likely to have four
outputs: one for each speaker. So, you will need to take the fader out of
the system for best performance. Try to trace the wires from the back of the
fader to the original radio. The PO may have already doctored (or butchered)
these wires as well. Then you will need to identify the wires to each
speaker, cut them and wire them into the appropriate output on the
replacement radio. In most cases, you will find the low side of the speaker
cable pairs wired together near the fader control. When you install the
replacement radio, make sure you separate these, and each output should be
in independently wired.
The original Becker, being a mechanically tuned radio does not need a
constant power source for the memory, as a new replacement radio will
require. You will need to find a source. Use a trouble light or multi-meter
to find +12V with the keys removed. There is a source on the ignition switch
or light switch. Make sure you fuse this line. A better place is the wire to
the dome light. Avoid routing the constant voltage wire around the clock as
the coil in the clock can induce noise the radio will pick-up. I recently
assisted a friend with an upgrade in his W123 ('79 300D) and we found a red
wire that went to the dome light and spliced into that. The confusion factor
here is that the switched +12 volts currently going to the Becker is likely
to be a red wire also, and is controlled by the ignition switch, so it will
not work for the B+ (memory) requirement of the aftermarket radio.
Look around for a blue wire. The blue wire that plugs into the Becker is for
the power antenna, if your car is so equipped. The brown wire is the
ground. I suggest a separate ground to a fresh source. A poor ground is a
common problem with updated audio installs.
Wires to mechanical Beckers:
Blue: Antenna
Brown: Ground
Black: Switched 12 volts
Wires to electronic Beckers
Pin 1 - off-set Ground, Brown wire
Pin 2 - Ignition + 12 V Black wire
Pin 3 - Illumination + 12 V Gray wire
Pin 4 - Constant (memory) + 12 V Red wire
On my W123 and others I have worked on, the speaker pairs are as follows
(yours may be different):
Left Front White connector,
(+) Gray w/ red stripe
(-) Gray
Left Rear White connector,
(+) Red/ black stripe
(-) Black
Right Front Black Connector,
(+) Green w/ black stripe
(-) Black
Right Rear Black Connector,
(+) Black w/green stripe
(-) Black
This is a lot of wiring, but done carefully and properly is worth your time.
When adding and splicing wires, I always solder the wires and cover the
splices with heat shrinkable tubing (available at Radio Shack). I believe
this is a better method than crimp on splice connectors (personal opinion).
Hope this is helpful,
Dan Steadman
1980 300D
1980 300TD Euro
Date: Wed, 17 May 2006 01:06:09 -0500
From: "Zoltan Finks" <[EMAIL PROTECTED]>
Subject: [MBZ] Wires to radio
To: "Mercedes Discussion List" <[EMAIL PROTECTED]>
Message-ID:
<[EMAIL PROTECTED]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
How many wires run to the back of the radio? I've got three hanging out of
the hole that used to be where the radio lived, but the PO left vacant.
I ask because the PO seemed to have a habit of screwing around with the
wires in the thing, and I'm not sure what he did (or was trying to do). The
cigarette lighter base is missing, along with the glove box light (the hole
for which has a few wires running out of it with crude splicings of speaker
wire onto them).
So I'm hoping that the three wires that are hanging out of the radio hole
are the three I'll need to hook up a radio. Sound right?
Brian
83 240D
