Hey all-own a super 300D that is a dream car (!) most of the time. About two weeks ago, was driving home at night and the lights went out. Other than peeing down both legs, the lights came back on after I turned the switch on and off. I'm trying not to drive it at night, but have noticed now that when I use the turn signals in daytime, all the gauges peg out and stay that way for about 5 seconds after turn signal goes off. Signals work fine on outside viewing, however, can't figure out why everything pegs out. Of course, the scary part is losing lights while driving on the interstate!!! Any ideas? Thanks

 

First thing I would check is the fuse for that circuit, oxidization on the fuses is common on the older mercedes, clean the fuse and socket up with some fine sandpaper. I'm no expert (clearly) but have fixed a few problems on my 1988 190d doing just this.

 

Okay, what's next-took out all fuses and replaced them and still have the problem. At night when the headlights are on, the battery light and gauges wobble and blink. what should I check next?

 

It seems like you probably have a bad ground somewhere. You're likely just going to have to start disconnecting grounds starting at the lights, cleaning them and reconnecting.

 

AAAAgh!!! But thanks.

 

I must say though that I am perplexed that the battery light blinks. It should only do that when the system is not charging. But that should also manifest itself as starting problems. And it should affect more than just the headlights and dash lights/gauges. Curious.

 

Drove it tonight and while the gauges blink/wobble, it doesn't generally create any problems with the exterior signals and lights. Just that curious blinking. I can say that it seems to synchronize as the speed increases. The faster the vehicle goes, the faster the blinking!! When I am dead stopped, no blinking, but the high beam light and seat belt light are dimly on...(not battery light)

 

Could it be a problem with your alternator? Put a multimeter across your battery and check the voltage, you should see about 14v. You could get someone to rev the engine a little and see if the voltage goes up and down. Just a thought, but I'm no expert or anything.

 

Agreed. Definitely an issue with the alternator/regulator. Have it tested.

 

okay took it to and old school guy that was intrigued by the problem-when the headlights are on, there is a ticking sound along with the fuel and temperature gauge pegging out. When I told him the ticking sound increased with the speed of the car, a little lightbulb went off. After he researched it a bit, he says in Fords it's called a constant voltage regulator for the instrument cluster, but no one local has it the durn thing. I called Mercedes in Memphis (i'm in NE Arkansas) and they said they'd never heard of that or the problem. So, does anyone know what the heck this thing is and where I can find a replacement? A part number even? New alternator a bit back, and that is checking good. Where from here...Thanks all