Headlight gremlin

[Dcraig]

One night I was driving home in the dark and the passenger side low beam went out, but the high still worked. I changed the headlight, but it still didn't work.

A few days later, it just came on.

Now a few weeks later, I went to switch on the fogs and they came on for an instant and went out, along with the passenger low beam again.

I've tried to move the headlight switch slowly to see it that was the problem, but it didn't do anything.

Any ideas?

TIA,

Craig

[MikeTangas]

Start with replacing the fuses. Head lights left and right (as well as high and low) are all on separate circuits. Not sure how the fogs come in to play, but I'd start there. With the intermitent history, then going out completely, I'd suspect a fuse that was on it's way out, and finally finished the trip.

D'OH, just dawned on me the CD (I'm assuming the CD since you posted in the diesel forum ) only has one light each side (dual fillament), might be the high/low are still one separate circuits though.

[P.E.Haiges]

Probably a fuse problem as that was what happened to me. The fuses are made of a lead and mate to a brass connection. The lead oxidizes and opens the circuit. You don't have to replace the fuse, just clean off the oxidation from the lead by scraping with a knife. For a more reliable electrical system, clean all the fuses. You should also clean the brass fuse holders when the fuses are removed.

This appears to me as a quality problem with MB. American plug in or bullet type fuses do not have this problem. Wake up MB.

P E H

[tcane]

The old VW bug uses the same type of fuse M-B uses and the VW always have lots of problems with the fuses blowing. Compared to the VW, M-B fuses are almost reliable - probably because M-B's alternator is a better source of elec. and the generous use of relays to lessen voltage surges (VW did not have relays, or if it did it was only one or two).

On your M-B, when examining the fuses be aware that sometimes the fuse looks OK but when you take it out it falls apart. This can cause an intermittent contact allowing the electrical current to flow, then at other times no electrical flow. If you suspect a fuse take it out of the fuse holder and inspect it, even if you have current as shown by volt/ohm meter and/or the the circuit works. Cleaning the fuse box connections is also a good idea, as recommended by P E H.

Also, the various headlight beams are on different fuses. I am looking at a fuse box info sheet showing what each fuse protects. High beam right is on one fuse, high beam left with the high beam indicator is another fuse, low beam right with fog light (singular not plural) is on another fuse, and low beam left is on another fuse. Your fuse box may be different than the one I am looking at, but the concept is the same - M-B splits up circuits with fuse protection for each headlight and beam intensity.

I would also add that having a water tight fuse box cover would probably help to control possible corrosion on the fuse block connections. Check the cover gasket for cracks, make sure it is in the groove completely, and look for any other problems preventing a good seal.

Good Luck!
Tom

[Dcraig]

Looks like I have another project to add to the long list.

Thanks everyone for your help. I'll let you know the results on Monday.

Craig

[Billybob]

Returning from a Florida road trip traveling north on the NJ Turnpike the same thing happened. Dash indicator lights up and a quick check finds passenger low beam out. Made it home, buy new bulb and started to replace bulb. Disconnecting three prong plug on bulb was difficult. Closer examination revealed that the plug/receptacle had been overheating and an open circuit developed in the low beam circuit. I bought two new pigtailed plug/receptacles and replaced both passenger side (failed) and drivers side (showed signs of overheating) solder spliced and heat shrinked , so far so good. P. S. I don't know if this plug/receptacle sub harness can be replaced as a unit -I would prefer that method but my field expedient method was best at the time. Check out the wiring/plug! Good luck P. P. S. The original bulb still works so I keep it as a spare in the trunk!