Any 123 Radio Wiring Expertise?
 

Purchased a Sony XPOD 410U CD receiver to replace the existing Kenwood KRC-860 cassette receiver in my '83 300D. Looks like the PO got the Kenwood for hookup into the car phone. For some reason the original MB speakers were replaced with no name JUNK, which is the real reason I've decided to replace the entire sound system. The new speakers are Polk Audio db 400 in front and Polk Audio db 525 rear.

Had to do a little corner trimming on the front speakers (easily with back and forth bending with vise-grips). The plastic dash speaker cover is a little snug on top of the center tweeter? but is not noticeable. Rear speakers went in easily after removing the plastic bellows which surrounded the original speakers.

When I removed the Kenwood I saw that whoever put it in did extensive rewiring. The normal blue, red and black wires are no problem but it's the yellow and orange which I can't figure out. The orange-white striped wire has a plastic marker which says DIMMER on one side and ILLUMI on the other.

That variable adjuster at the back of the shifter console would adjust the volume between front and back speakers. I can't figure out how it's tied in. Also I can't locate the rear speaker wires in this tangle. The color codes don't match and after I disconnected the battery I couldn't get a continuity check between any of these wires and the rear speakers.

Does anyone know where a radio wiring diagram is for the W123. I'd like to rip out all this crap out and rewire it.

I just put the GT520 in mine, and I used the diagram on this thread for help. Getting rid of the fader switch is pretty easy- just peel back the black plastic wire sheath and follow the directions on the thread. It has a good diagram that helped me a lot. I'm not sure the colors will help you, but the wire position may. You can use a small AA battery to find which wire goes to which speaker. The speaker will crackle when it is hooked up to the small battery.

And speaking from experience, tape the antenna connection really well if you are using a cable extension (I put in the XD-100 HD tuner). It fell out when I installed the headunit and was a pain to get out. Also, don't drop one of the two radio removal keys behind the headunit when you install it. It made getting the headunit out to access the antenna cable a PITA.

edit- that is a fader switch, BTW

New wires
 

I recommend abandoning the existing wiring and running all new wires. In the 123 body it's fairly easy to do, just lift up the carpets. I replaced the speakers with MB-Quart speakers, there's a thread here somewhere on that project. You can abandon the fader switch in the console and use the controls in the radio so that you have true 4-speaker stereo. I ended up installing a switch in the fader position and wiring it to my garage door opener remote (there's a thread on that, too).

Jeremy

also you can tell which lead is + this way. use a 1.5v batt- anything from AAA to D cell works. when connected to the batt, if the cone pushes out, the positive lead is on the + of the battery. if it pulls in, polarity is reversed.

orange-wh is for dash lights- will dim when headlites are on- can ignore or tie into the+ side of any lights under the console.
yellow should be switched ignition, red to batt. or vice versa.

I just did this in a 300TDt a couple weekends ago so the info is pretty fresh in my head. Those 4 speakers wired in parallel with a common ground will provide a 2ohm load to your new head's amp and it probably won't put up with that for very long, plus modern heads have fader controls onboard so I'd recommend definitely taking the factory fader out of the equation and getting all of the wires up to the radio where you wil forever have all the options you need. I didn't run new wires to the speakers - the factory wires were a heavy-enough gauge and all in good condition.

Here's the basics of the factory wires:

Brown = Ground -
Black = Switched Ignition +
Red = Always on + (memory)
Grey = Dash Lights (dimmer)
Blue = power antenna

The speaker wires you'll find behind the radio are;

Red+ Black- Left Speaker (goes to fader on console)
Green+ Black- Right Speaker (goes to fader on console)

To bypass the fader:
. remove the ashtray
. remove the two screws from the ashtray mount and pull that out
. the center console slides back an inch or two and can then be lifted. One mine, the front corners had to be bent slightly (be careful not to break anything) to come out from under the plastic bits and be careful with the back (the end closer to the armrest) - there's a pin at the very rear that goes into a hole in the console mount - if this pin isn't fully free of the hole and you yank up, you'll break something

There is a plug on the bottom of the fader unit that has 6 wires going to it - 4 speaker + and two common grounds. Pull the connector off the switch and snip the wires off the connector and then pull that entire sheathed bundle back up under the console into the hole behind the radio spot. I had to remove a large zip tie near the shifter and there was masking tape around a few of the wire bundles way underneath that I basically had to tug that bundle out of.

Once you have the whole bundle available, carefully remove the sheath from the wire bundle and what you need to do from there is pretty obvious. Clip the connectors at the ends of the wires you find joined and you'll end up with the original red, green, black, black set completely unhooked and 4 pairs of wires that go directly to speakers. I did some extra cutting at this point to make even-length pairs as they were all different lengths in the bundle so that the splice points weren't all in one place. I left the individual pairs different lengths, but do whatever works for you. You'll have plenty of wire to work with when you're done freeing them

I won't mention wire colors - they seemed to vary a lot from year to year and I know at least on mine, the colors were hard to discern anyway. The fronts on mine were pretty obvious; they were the pair that just disappeared left and right behind the dash - the rears disappeared back into the wire bundle under the console. A quick test of one of these pairs told me which one it was which made the other obvious. It was all straightforward butt splices from there on out and everything was good to go.

Great link! I found about a dozen radio wiring threads, but not that one. This is what I was looking for.

The fader is supposed to?
a) fade the dash lights or
b) move between the front and rear speakers as was improperly? wired on mine

Yeah, I'll be doing some ripping out tomorrow in an attempt to restore to original wiring. Thanks.

Nice....thanks

You mean to dim the SUPER bright 123 dash lights. :D

yeah- I would definitely use the dimmer function- otherwise the radio lites will blind you compared to others.

fader is for speakers....

EricLee31, thanks for the great writeup, especially concerning the fader wiring. ;)

I just wanted to add, that the "no name, junk speakers" are probably still better than the paper crap that was in there go begin with. Obviously, the MB buyer for those speakers was deaf and blind, or else he wouldn't have put such an embarrassment of a speaker into a Benz.

This is true- the MB speakers are pretty weak. :o The new headunit actually gives them some sound to work with, and they are very poor at moving air. The front ones give zero bass (4") and the rears (5.25") have close to zero bass. I have my headunit's fader at +8 to the back just to get any bass out of the speakers. Compared with the Pioneer ones in our Volvo 740, these sound like junk.

B- they have a tendency to go bad and ruin the sound from the headunit. My fader took out 3/4 speakers if it wasn't in the all the way forward position. Talk about no bass... :eek:

happy to help! I've been soaking up so much info from these forums lately, i feel like I have to give back whatever limited info I have so far. I just hope it helps someone in the future... places like this are gold for those of us who like to do things themselves.


It goes that way with everything, even late models. Most people think those sound fine, especially when they're new. My 01 330i has the factory "premium" sound... 10 Harman Kardon speaker setup, the works. Yup, paper cones. Those got replaced fast. ;)

Wire gauge was mentioned above somewhere, but I didn't see a particular gauge noted. What is MBs standard gauge wire for stereo speakers? If you have you car torn apart anyhow, would you replace these wires with someting heavier?