Hello guys! How are you all doing?

I'm having some trouble with my sister's w123 (introduced her to the mercedes magic a couple of months ago).

Last week she told me that her car had no high beams. It turned out to be a stuck contact in the selector at the steering column. I fixed it and got high beam at the left side. I replaced the fuse for the right high beam but got nothing. I checked the voltage at the plug and it turned out that there is good voltage (12.5 V) in the high beam cable, but as soon as I plug the lamp, the voltage drops to 0 V. I tried it using a known to be good lamp.

Also I noticed that its blowing the #12 fuse, which is not related to the high beams. This fuse covers the power window relay, part of the instrument cluster and the turning lights.

I'm kind of confused now...

I suspect it has something to do with a short circuit, but I rather hear your opinion before digging cables.

Any idea about this? I've been looking for a headlight wiring diagram, but I can't find it anywhere. I'm in Costa Rica now, so I can't wait for the factory manual in cd-rom to be delivered. Can anyone of you send me a copy of the manual on-line? I'll pay for it! I'm in a hurry, because this is my sister's daily driver.

Thanks for any advice!!!

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1982 W123 300D NA Euro, 300K Miles, 4-speed manual, 3.46 rear diff, early W126 front brakes, Penta rims with 205/60R15 FH900's, custom fitted (by me) audio system, more to come into the money pit... Soon to be installed: Bilstein HD, R107 front discs and 4-piston calipers, HD Suspension springs, wagon front swaybar.

Not with the #12 Fuse but with the headlights. My problem turned out to be corrosion on the ends of the fuses. Used a bit of fine sandpaper on the fuses and the fuse holder springs and problem solved. Seems that the corrosion would not allow enough current to flow to turn on the light.

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1983 Mercedes Benz 300D Turbo (Daily Driver)
1979 Mercedes Benz 300CD (Needs Lotsa Work)
1963 Chevrolet C10 Stepside Shortbed (Not Stock)
1999 Chevrolet Silverado Z-71 (Fun to Drive)
2007 Nissan 350Z (Wifes Car - Lucky!)

If you PM me with your e-mail address I can send the W123 diagrams that I have.

Not sure about the #12 fuse blowing, but the headlight issue sounds like a bad ground.

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'83 300D Turrrbo 295K miles

I've still got the same issue, with almost the same symptoms. Haven't checked the fuse though. I haven't gotten around to looking at it more, but Im going to have to soon,, as inspection is looming.

Thanks for your advice. I'll take a look at it.

I was thinking of a this issue, and I think that maybe there is a shortcircuit in the wiring harness that goes to the right headlamp. Maybe fuse #12 is blowing because the turnsignal cable is somehow doing a short somewhere. That could also explain the right headlamp issue...

I'll check it tonight and report back ASAP. Thanks!!

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1982 W123 300D NA Euro, 300K Miles, 4-speed manual, 3.46 rear diff, early W126 front brakes, Penta rims with 205/60R15 FH900's, custom fitted (by me) audio system, more to come into the money pit... Soon to be installed: Bilstein HD, R107 front discs and 4-piston calipers, HD Suspension springs, wagon front swaybar.