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I'm trying to troubleshoot some problems in the gauge cluster. I don't know where the ground wires are for that assembly. Mine is a 1983 R100RS cluster. I have figured out which one is the turn signal indicator light (#5) on the plug but I am not sure how to go from there.

My tach worked and then quit working the last time I had the gauge cluster off the bike to check the turn signal indicator light. Great. Didn't fix it and now I have one more thing to chase down.

I would think they would have a schematic telling what each of those pins and sockets goes to but I don't know where to find it.

Thanks for any help.

Chuey

The turn signal indicator is now working. It was a matter of cleaning contacts. I have concluded that the tach issue is not in the instrument housing. That, I say because everything seems as it was when it was working. Where are the wires at the other end of the harness? In other words, where do the wires that feed the signal to the tach originate?

Chuey

The pin assignments for the multi plug are shown on the BMW circuit diagrams and in the earlier Haynes Manual, I recently noticed that the diagrams in the latest manual don't have them (Doh! ). They differ from model to model. Don't have manuals to hand at the moment but, if it would help, I'll post the assignments later.

The tacho has three connections. One is a ground and a second is a 12v positive supply. Both of these come from the normal feeds to the instrument housing. The ground is shared with all of the lamps including the illumination lamps but excepting the Neutral, Charge, and Oil lamps. The 12 volt feed is shared with Neutral, charge and oil lamps. If the first group of lamps is working, you can infer that the ground connection to the cluster is sound and if the second set is working, you can similarly infer that the 12v supply as far as the cluster is sound

The third connection to the tacho is a wire that comes from one of the coils. It is attached to the connection between the coil and the points/ignition module.

Inside the cluster, the three connections are taken from the circuit board to the instrument with by three thin wires. These attach to the board with three small spades. The three colours are Red, Green and Black. Red is the 12v feed but I can't remember which of the other two is ground at the moment.

Hope that helps

Rob

Hi again,

the pin assignments are:

1. Not Connected
2. Neutral lamp -
3. Instrument illumination lights +
4. Charge Lamp -
5. Indicator repeater (1)
6. Oil Pressure Lamp -
7. High Beam +
8. Positive Feed
9. Not connected
10. Tacho signal lead
11. Indicator repeater (2)
12. Ground

Hope that helps

Rob

Thanks, Rob. I'll get a chance to look at it Thursday morning.

On my tach, as I recall, the three wires are red/green/brown. Of course, I'm color blind to reds and greens and sometimes think something green is brown. Good job by BMW is that I can clearly identify all three of those wires.

I think all I know about electrical systems has been learned right here on Boxerworks and as a result of working on my BMWs. Some of it is actually sinking in.

Chuey