High beam kicks off relay on 1992 T800

Discussion in 'Trucks [ Eighteen Wheelers ]' started by 57ringo, Apr 27, 2015.

  1. 57ringo

    57ringo Bobtail Member

    26
    1
    Dec 21, 2008
    Emporia, ks
    0
    I can run dims all the time with no problem but when I turn the bright lights on, the relay kicks off in about 45 seconds and stays off until it resets. I can unplug either side harness behind the headlights and it stays on. I put new bulbs in and didn't changed anything. I changed the relay with all the others and no difference. I'm stumped.....anyone know what might be the problem?

    TIA
     
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  3. GrapeApe

    GrapeApe Road Train Member

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    Jan 7, 2013
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    Are you talking about the circuit breaker or a relay? If it's the circuit breaker, then you have something drawing too much power. I'd first start by unplugging the headlights and see if it still does it. You can disconnect the headlights at the fire wall too, to isolate the problem to inside or out. Most likely some corrosion in a plug, check where the headlight harness plugs in, usually near the front behind the bumper.
     
  4. 57ringo

    57ringo Bobtail Member

    26
    1
    Dec 21, 2008
    Emporia, ks
    0
    I'm talking about the circuit breaker in the fuse panel. I can unplug either of the harnesses behind the bumper and it doesn't do it. I agree there is too much draw but unplugging one side or the other should have isolated it....right?
     
  5. GrapeApe

    GrapeApe Road Train Member

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    Jan 7, 2013
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    Not all of the time. If corrosion is causing a path to ground somewhere it is usually not a dead short, just an added load because corrosion has resistance. The added load is enough to kick the breaker when both lights are on, but take take the load of 1 light bulb out of the circuit and total current is less than the breaker, so it doesn't kick.

    At this point, you'd be better off using an amp meter to see if there is still current to the high beams with both plugs behind the bumper unplugged. Then you can also see exactly how much current each bulb draw when you plug them in.
     
  6. 57ringo

    57ringo Bobtail Member

    26
    1
    Dec 21, 2008
    Emporia, ks
    0
    ok thanks, I'll try that.
     
  7. Bigray

    Bigray Road Train Member

    1,135
    382
    Nov 23, 2007
    Tampa, Florida
    0
    I recently had a high beam headlight problem, what I found was chaffed wire @ the hood hinge, pulled the loom over it and no more problem.
     
  8. sailboatjim

    sailboatjim Light Load Member

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    Aug 27, 2014
    Boston, Mass
    0
    What is the circuit breaker rating?
    What is the current of the lights that are operating when the hi beam is on?
    If everything is stock then I would have to guess that the circuit breaker is weak or has been changed with a lower rating breaker.
     
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