2 replies [Last post]
lenweiss's picture
VBMWMO #8954
Joined: 06/21/2015
Posts: 3

There is a harness that includes a red wire (from the starter relay), a green wire (from the coils), a black wire (from the horn) and a brown wire (from frame ground). All 4 lead to the ignition switch.
In the course of removing my instrument cluster, I noticed the ground wire is not itself shield within the black wrap of the harness. Do you know if that is correct, or has something gone awry in the harness.

brook.reams's picture
VBMWMO #7701
Joined: 03/02/2010
Posts: 87
73 R75/5 Electrical and Wiring Photos


Here is a link to pictures I took of the electrical system when I removed the cables and reinstalled them. They may be of some help in answering your question.


If I understand your question, there is a cable that goes into the headlight shell and has wires that attach to the ignition switch inside the shell. You found a brown (ground) wire separated from the sheath that contains the other colored wires you mentioned. So the question is has someone mucked about with the wiring.

This diagram from MAX BMW parts fiche (#1) shows a four wire section that goes into the headlight shell.

That suggests (but I can't be sure this is the part of the harness you are referring to) that they were in the same outer sheath. That said, if the brown wire is the one outside the sheath, and since it is a ground wire, the original may have failed and another wire to ground added to correct this. Adding a brown wire that goes to ground is just as good as the original brown ground wire IHMO. So, my hypothesis is your wiring is functional since there is a good ground wire going to the ignition switch ground terminal.

You don't say if you have had any problems with the ignition switch or starting the bike. I assume that all works fine, but you were curious about the brown ground wire and it this was a symptom of a larger problem.

I hope this helps.

Brook Reams

I hope this helps.


Brook Reams-Arvada, Colorado
[Various Two-wheeled Vices, All BMW]
Web Site --> brook.reams.me

cc238's picture
la quinta, ca.
Joined: 11/17/2015
Posts: 17
73 R75/5 wiring

Does anyone have a good set of pictures for the wiring inside the Headlamp? I have acquired a post Luftmeister fairing model and need to sort out the lights horn and get rid of the electricians tape! Thanks

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