Horn and headlight out, everything else works

[larrynyc]

So I'm on the final steps of my winter project on my stock 1975 XS650B, and the engine starts fine, everything works, thanks to you guys. But I hit one final snag: the electrics. The headlight and horn don't work! I've disconnected and re-wired it five times and it's driving me nuts.

In detail, this is what does not work:

1. Headlight (both low and high don't work)
2. Horn
3. Little blue high beam light on instrument gauge
4. Right turn signal arrow on instrument gauge

Everything else works: Front and rear signals all work and flash appropriately. The instrument cluster illuminates properly when the headlight on/off switch is toggled, the running night tail light works properly as well. Brake light works with both front and rear brake. Start button works, kill switch works, bike runs fine. Little left turn signal arrow on instrument gauge works. Little red brake indicator light works.

The horn worked for a split second when I wiggled all the wires, then never worked again. The headlight worked when I tested it directly on the battery, but doesn't work when all wired up.

I sketched a wiring diagram on the computer showing how I've wired it. I noticed the browns and greens look similar, so I called them tan/dark chocolate, and green/dark green to differentiate: http://i.imgur.com/FPw6kBq.gif

What wires should I check before I throw out all the wiring again? Some of the wiring is brand new.

Main wiring harness = brand new.
Right switch = brand new.
Left switch = old.
Ignition switch wiring = old.
Instrument gauge wiring = old.

Any insight appreciated. Thanks!

 

[5twins]

Did you eliminate the RLU? If so, a couple wires in its harness plug need to be jumpered or the headlight won't work.

http://www.excess650.co.uk/tips & tricks.htm

 

[TwoManyXS1Bs]

Also check the wiring into that 3-prong headlight connector. They get squashed during headlight install, and can break right at the connector crimp...

 

[larrynyc]

Hello again 5twins! No, I did not remove any RLU, I don't think my bike year has one.

 

[larrynyc]

TwoManyXS1Bs -- I will check that next thing. But I'm still at a loss about the horn and the hi-beam indicator.

Now, I have an idea to temporarily rig the headlight by wiring it directly to the battery with long wires until I get the rest of the wiring sorted, would it damage anything by doing that?

 

[TwoManyXS1Bs]

It could, if the wires chafe and short. Myself, I'd find and fix the problems before adding more complexity...

 

[chizler62]

Have you adjusted the horn?

Posted via Mobile

 

[Brassneck]

Other than your turn signals, seems like everything else on the left handlebar switch housing is at the core of the problem...perhaps the ground is missing?

 

[XSLeo]

On the horn, power flows to the horn on a brown wire, through the horn out on the pink wire up to the button. The button grounds the pink wire to the switch housing. The ground path from the switch housing is through the bars, to the risers. On the bottom of the one of the risers is a black wire. This wire runs from under the nut to one of the upper tree clamp bolts. Through the steering stem, bearings to the frame, frame to battery ground cable to battery. If you e-start button works ok then you have a good handle bar ground path.
Grounding through the neck bearings isn't the best way. Somewhere along the line Yamaha realized that and instead of grounding that way they ran a black wire from the left side switch housing down into the headlight bucket and plugged it into the harness ground. I'm not sure just what year they started this.
On your bike I would instead of that wire from the riser to the clamp bolt I would run a wire from the riser back under the tank to one of the coil mount bolts. This will bypass the neck bearings. a much better ground.
On the headlight the on/off switch being on the right side should be ok, it's new right? On the left side where the dimmer switch is, could be the problem. Remove the switch housing from the bars. Power comes from the off/on switch on a blue/black wire. With the key on, headlight switch on check the voltage on the blue/black wire. Then with the dimmer in low check voltage on the dark green wire, in high the yellow wire. The blue /black should read close to battery voltage, the dark green and yellow should read close to battery voltage. If no power is getting to or through the dimmer switch the headlight indicator won't light. If no voltage on the blue/black wire remove the right side housing to check voltage on the blue/black at that end. Power comes to the on/off switch on the red/yellow wire. when on power goes out on the blue/black to dimmer switch and out on the blue wire to the tail light.
The turn signal indicator might just be a blown bulb.
Check these out. If power isn't where it should be check connections in the headlight bucket.
Leo

 

[larrynyc]

Update: finally had a chance to work on the bike again today.
Checked the voltage on the blue/black male connector from the left control that linked to the female blue/black from the left main wiring harness -- no juice at all with the right headlight switch set to On. (I could tell the on/off switch itself was working because the gauge illumination was on and the running night brake light was on).

I have now removed both the left and right hand controls to investigate this evening.

 

[larrynyc]

I thought there was a frayed wire somewhere. So I checked the continuity on the blue/black wire to the little blob of solder by the switch, it was fine. The green wire was fine too. The yellow was fine as well. But when I tested the blue/black on the end of the wire to the green or yellow -- nothing. So I think XSLeo is on to the cause -- it must be the high/low beam switch. I'll report my findings soon.

 

[larrynyc]

Upon taking apart the high/low beam switch, I saw some green, powdery residue and some brown rust-looking residue on all of the flat contacts, and some dirt on the little round pointy contacts from the switch.

I cleaned all of them with fine 800-grit sandpaper, and wiped with electrical contact cleaner. After reassembly, I tested the connections and now have continuity from the blue/black to the green, and from the blue/black to the yellow. Great! There was zero continuity before the cleaning.

I will have to wait until tomorrow to put it back on the bike, but the continuity test result is promising.

 

[TwoManyXS1Bs]

Excellent before/after pics Larry! Those will be very helpful to other members. Aged/corroded electricals are a common theme on these old bikes, and your pics display that well.

A thin coat of electronics grease on those contacts will ensure their longevity...