Topic: Electrical issue: No Juice on Br/W

[Patrick]

I am getting better at these electrical gremlins, but I'm not there yet....

The bike is a 1975 K5 750. I have juice on R at the switch and R/Y at the rectifier. Main fuse is good. The switch is aftermarket, found in a drawer in the garage, but since I kept it I assume it is not known bad. The juice on the red at the switch, however, does not seem to be carrying over to the rest of the electrical system. When I turn it to run I have a neutral light and nothing on the Br/W wire. Oddly, I also have no tail light. But on the Park setting (why this exists is beyond me) the tail light works fine.

So, bad switch? Or could something downstream from the switch, on the Br/W wire, be killing the circuit?

FWIW, the ignition switch is correct for a K5, but the wiring harness is from an F2 750. That means I had to switch out the plug on the wire harness to match the ignition. The wires are the same, however, except the wire harness has two brown wires that connect to the ignition switch instead of one. I spliced these BR wires together at the plug.

I took the switch apart and there does not seem to be anything in there that could go bad. The brass plates were shiny and the contact points were clean.

I have no problem going back and checking every wire (again), but I would like some idea what I'm looking for.

Suggestions, anyone?

Patrick

[Silverback]

Silly question, but just to be sure. Do you have a handlebar switch that allows you to turn the headlight on and off? Is it on? The Br/W wires are ganged at a connector in the headlight bucket. Is the br/W wire hot from the handlebar switch? If not, the wiring from the ignition switch is suspect. BTW, this is an independent circuit after the "main fuse". How does the headlamp fuse look?

[Patrick]

Headlight fuse is brand new, Silverback. There is no power on the Br/W wire at the switch (actually, with an F2 harness, the wire from the switch is Bl/O), but still no juice there. Probably because there is no juice on the Br/W wire at the ignition switch itself to go to the handlebar switch.

No, no on/off headlight switch. At least not connected. I have no juice on anything except the Bl and Bl/W wires. So I would have spark, if I tried to start it, but no lights or secondary electrical system. I just can't figure out where it is lost. I hate to buy an ignition switch it may or may not need.

It makes no difference if I disconnect everything from the Br/W wire. Still no juice. I am starting to wonder if there is an inherent incompatibility issue with an F2 harness and a K5 switch.

Back to the harness. I must be overlooking something.

Patrick

[Silverback]

Let's start from the ignition switch. You are getting the parking light, which is a direct connect to the main in this key position. So, the main is powered. At the wires exiting the ignition switch you should have power at the Black and the Br/W. If you don't, the switch is bad. Actually, there is some redundancy in the system with the Br/W and the Black wire being connected with a Brown/Red wire. It seems odd when looking at the wiring harness, but there is a place in the 4 pin Black wire gang for the Br/Red to plug into. These jumpers usually have a yellow indicator on the connector. That might get you going, but you need to fix the power coming out of your switch if it is faulty, or add in your own switch somewhere.

Just checked the wiring diagram and there is no redundancy at the headlight switch on 75K models, so you have an extra Bl/W powered wire somewhere.
Things to think about.  The black wire should provide power to the headlight through the black wire at the starter switch (Red/black after switch). Starter switches often break or work improperly over time.

[RAWNOG]

Im still trying to figure this out before I start reconnecting my harness and lights together. I have a 76 550f switch and a 75 550k harness, with no blk/r wire in harness, Im still trying to figure out whether the blk/r from the switch goes to br/w in the harness or not. It would seem so looking at the diagram because the headlight fuse is a br/r wire that turns into br/w which seems to control the headlight.

[Patrick]

OK, got it. The switch turns on only the black. The rest of the electrical system cascades from there, one segment at a time.

BTW, Raw, if your harness is like mine, a black wire will feed the headlight wire and the br/w wire. The br/w wire feeds the br. I had the br/bl leading to the br/w at the fuse, but I still had no juice on br/w until I connected it to black in the bucket.

Patrick