PeachParts Mercedes-Benz Forum - View Single Post - Looking for W123 wiring diagram. Headlamp issue.

jay_bob · #2 01-27-2013, 08:08 PM

I have a w/d for a 1983 240D but no good way to attach. I'm on a plane and on an ipad. So here is the system described in words. I am pretty sure this wiring is the same for all 123s of this era.

Headlight power comes straight from the battery to pin 30 on light switch. Be careful, this is unprotected power.

When the light switch is twisted to headlight mode, pin 56 becomes live and feeds power for both sides headlights to the combination switch. Power goes into the combo switch on pin 1, out on pin 3 of the C106 (big connector below column from switch), and pin 3 is live when the stalk is relaxed. Pin 2 of C106 goes live when the stalk is pushed for hi-beam, and also goes live when the stalk is pulled for flash, but in this case is instead fed from F6 via pin 11 when the key is on only.

Ok now on to the fuse box. Pin 2 of C106 is the low beam and feeds F13 (left low) and F11 (right low). F11 also feeds the fogs on both sides. This is looped back into the light switch on pin NSE and out on pin 58N, on to the headlight housing connectors.
Pin 3 of C106 is the high beam and feeds F9 (left high and dash blue light), and F7 (right high).

Kind of scary, two switches and probably 10 feet of the equivalent of #12 and #14 AWG wire before we hit protection. I couldn't get away with that in my world (UL 508A and others) but I digress. Just be aware of it and be careful when testing. I would slack the negative terminal on the battery so that just in case things go south while testing you can yank it in a hurry.

At the headlight housings,
Pin 1 is fog
Pin 2 is ground (common for high, low, fog)
Pin 3 is low beam
Pin 4 is high beam

Ok now all that said if you have no right headlight, high or low, nor fog the only thing in common is the ground.

If you have no right low nor fog on either side, but the highs are good then it's most likely F11.

Note these fuses are notorious for looking good but really are not. It should be SOP on a newly acquired vehicle to inspect the fuse box and if the fuses are not ceramic and copper then order a new set from the bird and re-fuse the whole box. Also take some brass cleaner or tarn-x and clean the brass tangs. Use no abrasives!

Also disconnect the battery and remove the fuse box to inspect the wiring in the rear. If you remove the lower dash you will find there is enough slack in the wire pack to drop the fuse holder down to the floor board for inspection.