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Thread: 1992 K-75RT headlight

  1. #1
    Dale Rudolph
    Join Date
    May 2009
    Location
    Medford, Oregon
    Posts
    579

    1992 K-75RT headlight

    I was going to add this to my previous thread about replacing a headlight bulb, but the problem with having no low beam while the switch is on has been fixed.

    I replaced the bulb, which did not fix the problem, I then opened up the left side switch, all wires were in place and it was clean.
    I then put a voltmeter to the high beam yellow wire and got a 12 volt reading. On the low beam white wire I got no voltage at all.

    My thought was that the problem was not the switch, but in the plug in that goes to the switch as there was no current to the white wire that operates the low beam.

    I decided to supply 12 volts directly to the switch ground and the white wire to see if the low beam would work, it did. This confirmed that the problem was no voltage getting to the low beam wire in the switch.

    I then put the switch back on the bike and then turned the switch on to make sure that the high beam, turn signals and horn still worked. The low beam now works.

    Is there a relay in the low beam curcuit that may have been jolted back into operating again from having 12 volts applied to it?
    If there is a relay, should it be replaced?

    While I'm glad to have the lights working again, It's not a good feeling when things seem to fix themselves.

  2. #2
    Registered User
    Join Date
    Apr 2012
    Location
    Los Angeles, CA
    Posts
    334
    There's no relay, nor even a fuse. You have a switch or wiring fault.

    There's a lovely wiring diagram here: http://www.verrill.com/moto/k75/images/k75_wiring.gif. Be sure to sanity-check it to make sure it's right for your year as well, of course. According to the diagram, the green/blue wire from the ignition switch feeds power to the right switch set. A white/yellow wire carries that power to the left switch set. The yellow high/low beam switch directs that current into either the white or yellow wire going to the headlight plug.

    Note from the diagram, the issue could be in the ignition switch. That green/blue wire doesn't do much else, so if it's at fault your lights could be wonky.

  3. #3
    Dale Rudolph
    Join Date
    May 2009
    Location
    Medford, Oregon
    Posts
    579
    Thanks again James.
    The wiring diagram you supplied is different from the one in my Clymers book, which is correct for my model.

    I also have a green/blue wire on the left switch. The green/blue also goes to the right switch.

    About two weeks ago, I had to drain and raise the gas tank for another reason and the bike wasn't started again until three days ago when I discovered that the light wasn't working.

    It may be that in raising or lowering the tank, the wire connection for the lights may have been moved.

    I will see if the low beam continues to work when the ignition switch is on, if it goes out again, I'll pull the tank off and check the connections.

  4. #4
    Registered User
    Join Date
    Apr 2012
    Location
    Los Angeles, CA
    Posts
    334
    Perhaps the work on the tank jostled one or both of the nine-pin connectors for the handlebar switches. Or, the disassembly and reassembly of the headlight switch may have corrected a fault there.

  5. #5
    Dale Rudolph
    Join Date
    May 2009
    Location
    Medford, Oregon
    Posts
    579
    The only other thing that may have made a difference is that while I didn't take the switch apart, I did spray some WD-40 into the headlight connections and rocked the switch back and forth.

    So far the low beam is working.

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