MZ 12v Rear brake lights

[lavrentyuk]

MZ may have finally boiled my head. Mechanically I'm just fine and have worked on many MZs over the years.

Electrically however I am challenged.

I'm figuring out how to wire in an extra brake light to go on the back of my sidecar. Of course, of course, MZ chose to put the front and rear brake light switches onto a negative circuit.

Trouble is my new rear light cluster shares an earth with brake, indicator and position lights.

Boiling my head figuring out how to do this.

[dave47]

I think your new light cluster is incompatible with the one on the bike, and you will have to modify one or the other. For example, you could fit a switching relay in the live wire to the bike's brake light and earth it permanently. Then use the brake switches to turn the relay on or off rather than the bulb directly. The sidecar bulb can then just be wired in parallel.
I must admit this is theoretical as I have never done this myself, although I believe this was a standard modification to the American MZ imports during the seventies, although it was for the purpose of fitting alternative lighting equipment rather than sidecars.

[DAVID THOMPSON]

Relay is your answer to this there is a web site on net that shows many ways t do this
i have been working on some other problems this week and my brain is badly locked up
so me trying to help right now is not a good time to have me help Dave

[lavrentyuk]

Appreciated - I'm in a similar position myself hence asking about what would normally be straightforward.

I decided to go with a separate brake light on the rear and have ordered the appropriate Hella parts - they do make nice light clusters.

By having a solo brake light I can continue to use the switched earth. Of course I'm making an additional bracket as it now has to carry two light clusters - the other one is a position/indicator combo.

I may be overengineering things a tad overall.