Can’t figure this 1979 electrical gremlin out.

[Mickster]

Headlight, gauge lights, neutral light, high beam indicator light, headlite stopped working warning light. None of it works. And I believe the gauge lights and neutral light should work soon as the key is turned on. Is that right?

Tail light, brake light, turn signals and turn signal indicators work fine.

I can get the headlight to work by jumping wires in the high/low switch with ignition on and motor not running so it’s not the headlight. I cleaned the high/low beam switch and all looks good. I also get power from the yellow alternator wire when the motor is running.

So, to narrow it down, it seems it’s all somehow connected to the gauge lights, and if that could be narrowed down to why they, and the other indicators, don't work we would have it, I think.

Any help is appreciated as I’m out of ideas.

BTW, the rebuild process I started in another thread is done. Motor got honed, new plus .025mm pistons and rings, valves re-ground, new valve seals and cam seals. Runs like a new machine.

Thank you guys and thank you forum. Could not have done it on my own. The tricks, tutorials and advice are awesome.

 

[5twins]

The instrument lights branch off the blue/black wire coming out of the headlight safety relay. They actually branch off before it gets to it's destination, the RLU. Sounds like your headlight safety relay quit. It should be sending power out to the instrument lights and the headlight (through the RLU) once the motor starts and trips the relay.

 

[Downeaster]

First thing I would do is pop the headlight out and check and clean all the bullet connectors and ground connectors in that rat's nest of wiring inside the headlight shell.

Most likely something has come disconnected or a ground is loose or dirty.

EDIT: Or what 5twins said...

 

[xjwmx]

To test the lighting relay you can jumper across the red/yellow and the blue/black at the relay. However the neutral light should come on with just the key, obviously. It's that dual relay on the right side

 

[5twins]

Yes, I don't know what's up with the neutral light. It's on a completely different circuit, not associated with the headlight or instrument lights at all.

 

[Jim]

Fuse?

 

[Mickster]

Following the above advice here is where I've gotten so far.

Unscrewed the safety relay from the frame to get at the wires easier, and unplugged and cleaned the plug where there are 6 wires, plugged it back in. I inserted the pointy end of my continuity tester and grounded the other end with the bulb in-between.

Started motor.
Yellow wire = light on
Two red/white wires = light on
Red/yellow, Blue/black and black = light not on
Shut down motor.

Checked the 4 fuses in the holder at the top of the battery and they look OK. However, if there is a fuse that works for those wires that aren't lighting up my tester I'll change it out. Is there another fuse somewhere else in the wiring. BTW, the wiring is pretty much how it came from the factory.

Broken relay? If so, how should I bypass it for the time being until I can find another one?

Thanks.

 

[Jim]

The relay could be part of your problem, but that doesn't explain the neutral light not working.
Here's how to bypass the relay. At least that will confirm/eliminate that as a problem...

 

[Mickster]

Jim, xjwmx. I jumped the two as you suggest with no luck.

Maybe I did it wrong. I jammed a nail into the plastic connector where the wires go right next to the wires, then clamped the two nails together. Should be OK right?

If I'm getting power from the alternator via the yellow wire with the motor running, which the test light showed is happening, the jumping of wires should of lit up the headlight after the motor was started, is that correct?

As posted earlier. The BL/B and RY wires did not light up my test light, I guess that test means no juice is coming out of the relay.

Juice going in, no juice coming out. Geeeeeez.

What should I try next.

 

[Jim]

Jim, xjwmx. I jumped the two as you suggest with no luck.

Maybe I did it wrong. I jammed a nail into the plastic connector where the wires go right next to the wires, then clamped the two nails together. Should be OK right?

If I'm getting power from the alternator via the yellow wire with the motor running, which the test light showed is happening, the jumping of wires should of lit up the headlight after the motor was started, is that correct?

As posted earlier. The BL/B and RY wires did not light up my test light, I guess that test means no juice is coming out of the relay.

Juice going in, no juice coming out. Geeeeeez.

What should I try next.

You did jumper the wires going into the bike's harness and not the wire going into the relay... correct? You want to eliminate the relay.... jumper the 2 in the bikes harness. Btw... with it bypassed, you don't need to run the engine... the headlight should work when you turn the key on.
If you did, that means the relay isn't the cause (I didn't think it was)... your trouble is elsewhere. You said you have no power at the R/Y wire to the relay? Correct? Start working backwards.... R/Y goes back to the fuse. You said you checked the fuse? Maybe check again?

 

[5twins]

Yes, the R/Y wire comes from the headlight fuse in the fuse box. No power on it means a bad fuse or no power being fed into the R/Y wire. Take the fuse out that bridges the two R/Y wires. Turn the key on and test both wires. One should have power, one should not.

 

[5twins]

Here's a little clearer picture of how the Special fuse box is set up. A red wire carries main power from the battery through a 20 amp main fuse on it's way to the ignition switch. From the ignition switch, a brown wire sends power back to the fuse box when the key is turned on. This brown wire splits 3 ways shortly before it gets to the fuse box. The brown continues to the fuse box but a R/W and R/Y split off it for the headlight and ignition fuses .....

If you get no power on either of the R/Y wires, fuse removed, key on, then that R/Y wire is broken, probably where it splits off the brown.