Newbie electrical help

[danielhowden]

The numbers on that unit suggest some kind of fuel pump relay. Where do the other wires on the "relay" go? That could help determine just what it is.

Kurt

So, the middle red wire and the two either side of that, blue and green and blue and yellow "I think" are the colours appear to come from the handlebar switch. The black wire with some blue sleeve goes into the loom and looks to be heading for under the front cover.

[Kurt in S.A.]

I have to ask. You said '76 R100S. Very few 1000cc bikes were built in 1976 or registered as 1976 models. Maybe some R100RS bikes were built. What's the VIN? Sort of important when looking at the wiring diagrams.

Kurt

[danielhowden]

I have to ask. You said '76 R100S. Very few 1000cc bikes were built in 1976 or registered as 1976 models. Maybe some R100RS bikes were built. What's the VIN? Sort of important when looking at the wiring diagrams.

Kurt

Ah ok, the VIN is 6062165

[Kurt in S.A.]

OK. Turns out that is a Mar 1977 build R100S, so looks like technically (?) it is a 1977 model.

Kurt

[melville]

The numbers on that unit suggest some kind of fuel pump relay. Where do the other wires on the "relay" go? That could help determine just what it is.

Kurt

So, the middle red wire and the two either side of that, blue and green and blue and yellow "I think" are the colours appear to come from the handlebar switch. The black wire with some blue sleeve goes into the loom and looks to be heading for under the front cover.

Yes. Green/Blue is from the key switch and is the power source for the signal side of the relay. Blue/yellow goes to the starter button and gets closed to ground when you hit the button.

Red and black are on the load side of the relay. The usual convention on a German vehicle is that red is always hot and wired to the battery. Black is switched hot--hot on the other side of a switch from red.

[Kurt in S.A.]

That black wire should go from relay 30 to starter terminal 50.

Kurt

[Rob Frankham]

Red wire - mI agree with Mel that the wire will go to that terminal space on the relay socket but the terminal must be 87, not 87a or 87b. A five terminal relay with a 87a or an 87b terminal will not work as a starter relay in a bike of that year (or any year up to 1984)

Lucar connection the the starter solenoid - Kurt is right, the wire from this connector is black and goes into the loom connecting to terminal 30 on the starter relay.

Rob

[danielhowden]

Sorted!

Thank you for all the comments and help. It's so much easier to "talk" to people. So yes the red wire did go into the connector block on the starter relay and I found a black wire behind the front cover that goes through to the starter motor housing from the front.

The loom is now live and the starter motor turns the engine.

I'm so excited - just a few more things to do before I can try to start the bike.

Thanks, Daniel.

[melville]

Happy happy happy!

Nothing like that first NANANANANANANANA.

Except for that first NANAVROOM!

[danielhowden]

Just checking - I've not worked on a BMW before. These lights look right for a stationary engine I think?

PXL_20221001_141229659.jpg (1.41 MiB) Viewed 708 times

On the indicator switch by the throttle is down supposed to light the right indicators?

Lastly, I'm not getting the brake failure light to come on. I understand that if there is no fluid in the reservoir then it should come on, also if the wires are taken off it should come on right? Neither of these options bring the light on and I did check that the bulb was ok.

Thanks.