1974 450SE electrical problems

[witty]

No 5 fuse shorts out immediately on replacing when turning lights on.  where to look first?

Nothing that relies on that fuse is working

Thanks
Allen

[jmperkins]

We need more history / details...what else is on that circuit along with the headlights. What have you changed or replaced tht is on this circuit? There is some kind of short but you probably figured that out.

Take care,
Joe

[witty]

thanks Joe

this fuse controls the following circuits:

parking/tail /standing light right /license plate /dash board /hazard warning flasher,
/shift indicator /head light cleaning unit.

Was all working as should until yesterday and nothing was interfered with at all.

Cheers
Allen

[koan]

         .... when turning lights on.

Must be either front or rear parking lights or their wiring and not any of the other things off that fuse.

Headlights and tail lights unplug. Unplug them both, if the fuse still blows short is in the wiring loom. If fuse doesn't blow plug either front or rear lights in to see which is at fault.

If it is the loom a likely spot for a short is anywhere loom passes through sheet metal.

Rare possibility is the light switch but that's doubtful.

[witty]

Thanks mate

Will try and come back to you

Cheers

[witty]

koan

Found out every time i connect the 2 pin connector for the number plate lights, the no5 fuse blows.
Have checked all connections and light sockets for short in tail light circuit boards (left and right) and found no problems. Have checked the number plate lights and all working and intact, no problems there.

With license plate disconnected, fuse stays intact, all lights are working fine, except for the indicator and brake lights on drivers side rear, which were working okay before this issue, the front indicator works, the rear reversing lights are ok both sides.

The handbrake light stays on all the time, never done that before.

I was told by an auto electrician that mercedes have the worst systems of all vehicles. I am beginning to agree with him.

Any ideas ?

[koan]

Found out every time i connect the 2 pin connector for the number plate lights, the no5 fuse blows.
Have checked all connections and light sockets for short in tail light circuit boards (left and right) and found no problems. Have checked the number plate lights and all working and intact, no problems there.

Did you check both sides of the unplugged number plate light to earth?

With license plate disconnected, fuse stays intact, all lights are working fine, except for the indicator and brake lights on drivers side rear, which were working okay before this issue, the front indicator works, the rear reversing lights are ok both sides.

Symptoms are a bit weird. Did the indicator and brake lights start not working same time as the fuse started blowing?

There is 14 pin connector in the boot somewhere, maybe that's worth a look

The handbrake light stays on all the time, never done that before.

How's your brake fluid level ? Think it and the hand brake share the same light

M-B wiring is excellent, lots of decent sized silver plated plugs and sockets, only problem is finding a correct wiring diagram, I have four for my vehicle and none of them are right.

[witty]

Koan

Found the light short, some cowboy had removed the boot lock and when they put it back they squashed the lead between the two plate lights, made new harness and all is well. Thanks.

You are correct, the handbrake shares the light with the master cylinder warning lights, checked the connections and cleaned, light now goes out.

Happy now, thanks for your input
Cheers
Allen