As I was going to work today I noticed that the fuel and engine temp gauges did not work. After a deeper look, the turn signals, brake lights, hazards, and cruse don't work.

I replaced the 8A #12 fuse. Brake lights and gauges work. Hazards don't work and using the right turn signal blows the fuse.

All the bulbs are good, there was no smoke from anything, and the brake lights don't blow the fuse.

Any ideas? I can't find anything unusual and a review of the wiring diagram gave me nothing.

Any ideas from the electrical masters?

Remove both turn signal bulbs and check the housing and all the connections to and from the housing for a break in the wiring or corrosion at the bulb. If the wiring to and from the switch is good (likely), then the problem has to be either the switch on the column or the sockets/wiring at one of the lamps.

You can also disconnect one of the bulbs (either front or rear) at the plug and try to blow the fuse, again. If it remains intact, you're homing in on the culprit.

If it still blows the fuse, then disconnect the other bulb (and reconnect the first bulb) and try it again.

If it still blows the fuse, disconnect BOTH bulbs. Try it again.

If it still blows the fuse, the problem is most likely in the switch.

Pull your hazard switch and check it for shorts. Your turn signals go thru that switch.

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C

Mine blows the same fuse ever 2-3 months at random. I have no way of tracking it down. I love the W123 but whos bright idea was it to put the BRAKE lights on such a common circuit. Now a days they are independent of anything else and each other.

__________________
Adam Lumsden
(83) 300D
Vice-President of the MBCA International Stars Section

I once had a variety of electrical problems relating to the headlight connector shorting to ground. It was a paint to find and I had to resolder it. Something is shorting to ground obviously. Do the checks that Brian outlined and, clean and check all ground connections and report back.

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1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair

I'll add my suggestion to uplug the connector near the turn signal housing. If that eliminates the short it could be a bad socket or wires to or in the housing.

Also, check the connector itself for signs of corrosion while it is apart.

Pulling the turn signal lights did nothing. I also noticed the dome lights (front and rear) don't work.

I'll spend more time testing the hazard switch and tracking down this gremlin on saturday.