Still havent solved the problem yet. I tried using a jumper to see if the voltage was low or not, which didnt seem to be the case. I also switched out some fuses, still a no go. Next step is to change the bulbs to oe, because the ones that are there are some cheap-o kragen brand.

Takedown, the OEM is Osram Sylvania. These bulbs/lamps are available at various auto supply stores. Pep Boys used to carry them. So check locally before placing an order online or buying them at a MB dealer. It's critical that they are the correct wattage; otherwise the electrical system may malfunction. Check your Owner's Manual for the design wattage of the various lamps.

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Fred Hoelzle

This morning, I removed the fron left turn signal bulb from the white socket and reinstalled it.
No problem anymore.

I will replace the socket anyway, because I find some crack on the white plastic.
One pin hole on the black plastic that accepts the pin on the white socket has greeny rust. But I do not know what to do for this.

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

thakdown and ktlimq;

If the dash arrow comes on when the lights are turned on then the front or possibly the rear turnsignal bulb is not grounded. To find out which it is, turn off the turnsignals and turn on the lights. Take them out one at a time and see if the arrow goes out. The bulb that turned out the arrow when removed is not grounded. The problem can be in the socket (the metal sleeve that holds the bulb in) or in the ground wire for the socket. To prove that the ground is the problem, use a jumper wire connected to a GOOD CLEAN ground and touch the other end of the jumper to the shell of the bulb while it is turned on.
I use a 12V test light to check things like this. If you conect the test light clip to a good ground and probe the shell of the bulb with it on and the test light comes on (usually dimly) then the bulb is not grounded.

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84 500 SEL (307,xxx miles)