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Electrical help

Discussion in 'The Garage' started by Tom, Nov 12, 2017.

  1. Tom

    Tom XS650 Enthusiast

    Hi guys, I’m currently working on my ’79 XS650 project and I’ve got to the wiring stage which has become a nightmare. The bike starts, runs and stops well but I’m having issues wiring in the headlight, turn signals and new speedo (back lit, indicator light, high beam light). I don't think there's power getting to the front end of the bike where i need it..

    I have a wiring diagram, test light and other tools but I’m really struggling with wiring things up. I think the PO has messed around a lot with the harness and hoping you guys can help?

    A bit about my bike – PMA, new battery, 3 wired blade fuses (20, 10, 10),

    What works:

    • Brake light
    • Horn
    • Starter motor
    • Kill switch
    • Ignition

    What I’m struggling with:
    • I have constant power to a couple of brown wires coming out of the two harnesses up at the front of the bike
    • I have no power to what I think is the headlight yellow wires when ignition is switched on
    • Do all grounds work the same? Or do some work for specific parts of the bike?

    I’m good with mechanics things but wiring just drives me nuts…

  2. XSLeo

    XSLeo XS650 Guru

    Up in the TECH section you will find a list of topics, Scroll down to the Electrical. Then Find the thread "Some Wiring Diagrams" Find the one for your bike.
    Use this diagram to trace wires from where the start after the key switch to the switches, items the switches feed. to ground.
    All grounds lead back to the battery. Yamaha uses black wires as ground.
    On your 79, stock it had 4 fuses, one main fuse of 20 amps and three 10 amp fuses to run everything else. On your headlight power flows from the main switch to the lighting fuse on a brown wire. This brown wire is sliced onto a red/white wire, a brown wire and a red/yellow wire. These three wires go to the three fuses under the seat. The r/y is the lighting. It feeds power to the safety relay on a r/y. After the S/R the wire is blue/black, this wire runs to the reserve lighting unit. Most get chucked. Unplug the plug to the RLU and ad a jumper from the L/B wire to Yellow/blue wire, This bypasses the RLU so the headlight on off switch works.
    There are ways to bypass the light checker and flasher canceler unit. Most of these devices are trouble just waiting to happen.
    At this point I might just strip out the wiring you have and start from scratch. Might be easier than screwing around with the cobbed up stock harness.
    In the "Some Wiring Diagrams" thread mentioned above #4 is the one I like. It shows a basic points set up with stock parts. Boxes have later model changes.
    Start upper right corner.
    This diagram deletes all the excess stuff you don't really need.
    If not, studying the stock diagram and using it to find the wires that go to the items you want powered.
    peanut likes this.
  3. 5twins

    5twins XS650 Guru

    On a '79, the headlight works through a safety relay. It won't come on, get power, until the engine is running, or at least been cranked over several times. The safety relay has a wire (yellow) running to the alternator. When the alternator starts spinning and putting out a charge, that trips the relay and powers up the headlight. Do you have an on-off light switch on the right handlebar control by the throttle? The U.S. spec model did not. '78 was the last U.S. model to get the switch.
  4. Tom

    Tom XS650 Enthusiast

    I swear the headlight used to work once ti turned the key and the ignition was engaged. Maybe i'm imagining things. No, the bike doesn't have a on/off switch for the headlight. The brake light turns on once the key's turned on too. Does that tell you anything?
  5. 5twins

    5twins XS650 Guru

    It's normal for the tail light to come on with the key. It's wired right into the key switch. Even if you had the on-off switch on the handlebar, it wouldn't control the tail light. I didn't like that on mine but couldn't "fix" it without a bunch of wiring changes, maybe a different key switch too. So I just put an L.E.D. tail/brake light bulb in. That's the only L.E.D. bulb I have on the bike but I feel it's the only one needed. The tail light is the only thing that comes on with the key and puts extra draw on the battery, none of the other lights do. They (headlight, turn signals) only get used while the bike is running so there's no problem with them drawing on the system.
  6. Tom

    Tom XS650 Enthusiast

    I've had another chance to look at the bike and I'm currently getting constant power from the green and dark green wires from the left hand control switch when the battery is connected and ignition is off - see pic. Is this right?? I don't think so, so what could cause it?
    From my wiring diagram, green from control switches should be high beam and dark green should be turn signal?? image1 (1).JPG
  7. gggGary

    gggGary Cara Mia!!

    For +12 to show there it has to be coming in through one of the wires in the 6 wire plug, but you are right iggy off there shouldn't be any live wires in that plug. check that the turn signal switch has been canceled. push in at center position.
  8. 5twins

    5twins XS650 Guru

    Yes, the green (low beam) and dark green (right turn signal) are wires running out to the components. You need to find the wires that are sending the power into the switches. The Hi/Lo switch has a blue/yellow and blue/green coming from the reserve lighting unit. There is also a yellow/black but the diagrams don't seem to show where that comes from. The turn signal switch has a brown/white from the flasher relay and a yellow/red from the self canceling unit. The battery seems to be feeding some of those wires power all the time.
  9. xjwmx

    xjwmx XS650 Guru

    FWIW, for incandescent tail/brake combo lights there are at least two that will fit the socket. One uses more power and has a brighter taillight but the difference between brake and tail is not as noticeable. The other uses less power and has a dimmer taillight but has a more noticeable difference between tail and brake. That is the one I use. The bulbs have different numbers, not hard to find for anyone interested.

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