Black instrument wire ID

[mattcfish]

Putting an Acewell 2853 speedo/tach on a 1975 R90/6. It appears my wiring is more closely matched to a 74. I've got everything figured out accept....... I have a solid black wire going to the #10 terminal on the square instrument pod plug. Does not show on my Climber or Haynes manual. Anyone know it's purpose?

[melville]

My bike is a December 1974. I opened the instrument pod, and using that and my Haynes wiring diagram I come up with:



1. Hot for turn signals
2. Ground for oil pressure light
3. Hot for instrument lights
4. Ground for charge light
5. Ground for brake fluid light
6. Ground for neutral switch
7. Ground for high beam, dash lights, turn signals
8. Hot for high beam indicator
10. No connection in the pod
12. Hot for brake fluid, neutral, charge, and oil pressure

I didn't disassemble the plug to see if there was a wire to #10, but it served no purpose in the pod. By DIN convention, a black wire is generally 'switched (ignition) on hot.' Can you power up, and check voltage to ground on that one? Does an additional hot help for an Acewell?

[chasbmw]

Did your bike have earth wires to the front indicators?

If not then your wiring is likely to be 74

[mattcfish]

I was told it was the points ground. Strange that it goes to the instrument cluster of a mechanical tach bike.
Was this an early wiring retrofit for future electronic units?

[mattcfish]

Did your bike have earth wires to the front indicators?

If not then your wiring is likely to be 74

No grounds to the signals originally. According to the numbers the bike was built in 9/75.
She originally had small PR tubes, small cam seal, small cylinder bases, but large 11mm flywheel bolts. And now 1974 wiring.
Frankenbeemer right from the factory.
Did I mention that the bike is listed as a 76' on the title.

[Jean]

75? 76?
My R100s, BY 9/78, is listed as a 1979 on the title.
Must be SOP...I think September must be the "first month of the new (vehicle) year". Also a tricky time for any vehicle coming from GERMANY, at least. You are always confronted with "which schematic to use..." and lots of OTHER mysteries.
Look at schematics for both years and choose the parts that match.
I'll see what I can find. I have a lot of old "Paper".

[r75bitsa]

Advrider covers the fitting of an acwell to an airhead, can`t remember the model# but it would be close.It has the black
wire as a common earth for pin# 7 has the wiring configuration as well. Headed fitting an acewell speed/tacho to an airhead.

Regards

[Jean]

Must be something that someone added (are you the only owner?) as BROWN is the ground lead on DIN wiring.
If another instrument accessory was added earlier, it possibly could be a ground however.
I'd replace it with a brown wire if it's to be a ground tho...or get some electrical tape in colors and wrap some brown rings around it at the ends.

[Jean]

I found an old schematic, this is going to be a surprise to you.
A BLACK wire is shown coming off the starter relay and going into the headlight shell...and NOT being connected to ANYTHING.
OR, in other words.
DON'T USE IT FOR A GROUND!!!!!!
No clue what it's for tho.

[r75bitsa]

Black goes to the starter solenoid and where it goes into the headlight on US models, the light relay. Uk delivery doesn`t have the black. Something to do with turning the headlight off while cranking over.

Regards