Please help with electrical problem, 92 300E *SOLVED
 

After a recent rainstorm, I lost power to my lights, including brake lights, the gauges and tachometer don't work, the rear interior light doesn't work nor do several dash warning lights.

I checked the fuses and found that several fuses are not being supplied with power. The lights work only if I use the switch.

Also there is a relay in the box behind the fuse box that is buzzing with the engine running.

I removed the under dash panel and carpeting on the drivers side to try to trace power from the ignition switch to the fuse panel but haven't found anything yet.

I found a post about a similar problem but no solutions.

This seems very strange, such a major power interruption should not be too hard to find but I'm not sure if I'm on the right track.

Any help is very much appreciated.

Acky

What happens if you wiggle the key on the "run" position?



Joe

Could it be corroded grounds?
 

Check your grounds for signs of rust or corrosion. If you find any - unbolt, wire brush, then reassemble and coat with dielectric grease. This is the easiest "first step" that I can think of.

Good Luck,
Troy 1995 E420

Well Joe, I just tried to wiggle the key again, more aggressively this time and I reached around to the back of the ignition switch to try to wiggle the electrical plug connector there and the result was no change and the buzzing from the relay continues while the engine is running.
I want to trace the wires from the ignition switch to the fuse box but it’s a mess of wires and at this point I haven’t been able to identify them.

As for ground problem I guess I can search for a ground for these related circuits but the hot side of the fuses have no power so I suspect an open circuit somewhere before the fuse box.

Thanks guys,

Acky
:confused:

Try checking the electrical connector near the battery. The battery positive has a 5 or 6mm wire that is connected to a terminal block which in turn feeds the alternator and the vehicle with circuit 30 power. Rectangular with 3 connections, 2-10mm bolts and one phillips screw if memory serves me correctly.

Might be loose or slightly corroded, always a good starting point.

electrical problem solved
 

Thanks everyone for your help.

Gilly from Hotrods forum solved the problem for me and I'm still a bit dizzy after all this.

Somehow a hairline crack in fuse #5 caused all the related problems, I don't see how it could affect other fuses but it did and replacing fuse#5 fixed it.

Thanks to Gilly I will put it back together sooner and better than it was due to other problems found.

thanks all,

Acky