Hello all.

I am working on my W123 83 300TD. Right head lamp is inop. Bulb is good, fuse doesnt have power. Fog lamps also inop. Seems as though right lamp and fogs are on same fuse.

Looking for wiring diagram to help shed some light. Searched for info but have not found a thread that was helpful.

Other suggestions?

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83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.

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.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Wow,

Fabulous reply. Thank you. I do have a working high beam, it is only right-low and both fogs that are inop. The fuse doesnt show power at all. I will test again.
I just purchased some copper fuses with plans to replace the lot. I will clean the contacts in the box after disconnecting the battery.

With out looking closer, it isnt clear where the terminals and other references mentioned are, but once poking around it may make more sense. I hope the connections are labeled as you mention. This would make it easy. Your description is reasonable.

First step, I'll clean the fuse box terminals and replace ALL the fuses.

Who is "the bird" that you mentioned I should get fuses from? I can only assume this is a slang name that means nothing to me at the moment.

I'd love to get a copy of a wire diagram at some point if possible.

Thanks again for the help. This gets me closer than I was this morning.

__________________
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.

I believe I got my copy of the diagram at startekinfo.com, there are 2 documents. One is a schematic (they call it the electrical troubleshooting manual or ETM) and the second is a series of photos and captions that identify the devices and connectors, called the component locations.

The bird is Pelican Parts, the sponsor of the site.

C106 is the big rectangular connector near the steering shaft under the dash. The harness coming down from the steering column switch lands on this connector. The 123 has a very simple electrical system, everything is right there and easy to see under the dash. There is another big connector under the dash, that is C104, that connects the entire rear of the car into the under dash harness.

The lower trim panel on a 123 is easy to remove, 3 cover plugs on the top edge, remove the 3 screws behind the plugs. Then 2 quarter turn plastic fasteners at the lower left (near the e-brake) and lower right (near the go pedal). Once you have that off you can see everything under the dash.

The light switch removes by pulling off the knob and loosening the big nut. Then grab the switch from behind and give the switch housing a twist to release the ears from the dashboard and it will drop down. There should be an insulator over the terminals. Be sure it is in place before dropping out the switch, you don't want to have the 30 terminal hit metal.

Good luck and be safe. But very first thing I would do is check fuse F11, I suspect you won't have to go much further to get lights back.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Thanks Jay bob. will do and will report back as I am not fond of 'dead threads'. Those with same symptoms and no description of success.

__________________
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.

Trying to locate info at Startek with little success.

This page is a dead end as there is a 'plug in' I do not have. No idea what 'plug in' I need.

Mercedes Video for Netscape Communicator

Ha! Ignore the plug in warning and hit the little "continue" at lower right.

here is the wiring diag. Not sure if link will worky.
http://www.startekinfo.com/StarTek/outside/12265/disc_2/program/ETM/83_300.pdf

__________________
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.

Easy fix.

swapped Fuse 11 with a new copper 16amp (red). Fogs and right low working fine.

Thanks jay.

I had planned to swap all the fuses and had recently ordered a set.

__________________
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.

This post is 6 1/2 years old, but still a winner. I've been searching for a schematic of my 300D for a long time. Many electrical gremlins hiding and I now have a map of their lair!!

Thank you for this.

cheers!!