electrcal problem
 

driving home from work the other day the instrument cluster went dead....also so did the brake lights/turn signals and headlights....battery is charging and the radio and interior lights still work....im thinking a relay....all of the fuses are good

any ideas of where to start?


thanks

What car is this? Sounds like a loose connector behind the instrument cluster.

it's a 1983 300sd

There is no common fuse or relay that controls all of these components on the SD.

My suspicion is that the voltage regulator is intermittent due to worn brushes. Sometimes you'll get proper charging voltage...........and sometimes you won't.............usually at night with heavy current demand.

When the problem happens again............check the battery voltage at 2000 rpm............my suspicion is that you'll find low voltage (10V or less)............

I do not have a schematic of your car. My initial suspicion would be the loss of a general power feeder. To many things are down. Forget that the fuses are good. Get a meter and see if you have voltage reaching the fuse panel first for those functions. A twelve volt test light would suffice as well.I have had to deal with the power wires split off the main supply system system to service certain things myself on 123s before. No reason I can think of presently that this could not apply to your series as well. Also a total ground loss but my feeling is in your situation the starter would not work.
The headlights for example are grounded up front I believe to the body shell. That would require two grounds bad at the same time. Not too likely in my opinion. So that eliminates a ground in the instrument cluster I believe. Let us know what you find. Also a load relay may not be turning on if your car has one. Now it could have a bad ground for example. But once you find out there is no voltage present at part of the fuse panel you should be able to start working backwards towards the battery. If the glow plug light comes on it is not the keyswitch in my opinion. Keep the forum informed as you go along or what was found. These electrical gremlins might become more prevalent as our cars continue to age.

So much will depend on your comfort zone and previous experience when chasing an electrical gremlin. On the otherhand one way we get better is by attempting something we may not have done before. Enlisting a friend with more knowledge also is a valid approach.

I should expand this a little more perhaps. Each headlight is separatly fused probably for safety. Also for safety they are separatly grounded. Not positive of the separate individual grounds just suspect it. You are in all probability not getting voltage delivered to the fusepanel.

thanks....i will start the process....also to add to the things that DO work are the windows and sunroof....it seems that everything i need to work to be legal to drive are the only things that do not work....frustrating