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Light problem

Discussion in 'The Garage' started by Demps, Nov 18, 2020.

  1. Demps

    Demps XS650 New Member

    Hey, my first post here. got 1981 XS 650 and I recently burned out the main fuse when a screw came loose from the generator brushes. When I discovered that problem I replaced the screw and got it running again but discovered that the head light circuit was dead. I suspected the reserve lighting unit so got one on ebay but no dice. Also tried connecting the blue black to the blue yellow to bypass the RLU but nuttin. So I went over the wiring diagram to try to track the problem and saw that a yellow wire comes from the generator to the safety relay before the RLU. Any ideas on how to test where the problem is? Thanks
     
  2. 5twins

    5twins XS650 Guru Top Contributor

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    There is a separate headlight fuse so I'd check that first. Once that is verified good, start tracing the headlight power path. A red/yellow wire carries it from the fuse to the headlight safety relay. Once the relay is tripped (by starting the engine), power should flow out to the RLU on the blue/black wire. Be aware that the headlight isn't going to work or come on until the motor is running and that relay is tripped. That yellow wire you found is what trips the relay once the bike starts, AND starts charging. If your charging system has failed then no voltage will go through the yellow wire and trip the relay. So, you should probably perform the simple charging system check too. Clip a voltmeter to the battery terminals and start the bike. Voltage should be around 12 at idle and go up to the low to mid 14's when revved to 3K.
     
  3. XSLeo

    XSLeo XS650 Guru Top Contributor

    Have you tested the bulb?
    Leo
     
  4. Demps

    Demps XS650 New Member

    Thank you both. Yes bulb and fuse check out fine. The entire lighting circuit is out which includes the instrument lights. The generator has been working well until the loose screw shorted the system. . I'm thinking the yellow wire from the generator to the saftey switch is not sending the signal that the bike is running. Is that possible?
     
  5. Demps

    Demps XS650 New Member

    Oops never mind. 5twins you were correct. I rechecked the charge at the battery and it’s 11v no juice from the generator. Out of the frying pan.....this is much worse. This bike doesn’t like me.
     
  6. 5twins

    5twins XS650 Guru Top Contributor

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    Yes, if you're not charging at all, no voltage will be sent out on the yellow wire so the relay won't get tripped.
     

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