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No headlights

Discussion in 'Electrical & Audio' started by Bill-W, Sep 15, 2020.

  1. Bill-W

    Bill-W Junior Member

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    Location:
    Southern NH
    First Name:
    Bill
    Truck Year:
    1986
    Truck Model:
    k20
    Engine Size:
    350
    My headlights dont work but I can make them come on when I power them directly. I checked the dimmer switch and there isnt any power getting to it. Does the power come from the fuse panel to the dimmer switch to the headlight or from the headlight switch to the dimmer switch? What is the best way to determine where the problem is?
     
  2. eskimomann209

    eskimomann209 Supporting Member Supporting Member

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    Truck Year:
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    Truck Model:
    C10
    Engine Size:
    5.3
    Is this one of them furds?
     
  3. Bextreme04

    Bextreme04 Full Access Member

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    I think it goes battery-> fuse-> headlight switch-> dimmer switch-> lights.... it’s going to depend on year also. There is a thread on here somewhere that has a ton of wiring schematics that could tell you for sure
     
  4. Matt69olds

    Matt69olds Full Access Member

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    GMC 1/2 ton
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    455 Olds
    I assume both high beam/low beam are out? Does the indicator for the high beam come on?

    Power for the headlights comes from a heavy red wire protected by a fusible link. I don’t have a manual here, so I don’t know if anything else is protected by the fuse link. From there, it goes to the headlight switch. The headlight circuit is protected by a internal circuit breaker. Power comes out of the headlight switch on a light blue or yellow wire to the dimmer switch. From the dimmer switch power comes out on the light green (high beam) or light brown or tan (low beam).

    if the high beam indicator on the dash works, you know you have power at least to the dimmer switch. That means the problem is most likely underhood. Start by checking for power at the dimmer switch on all 3 wires, they are arranged like this -_- . The lower middle terminal is going to be yellow or light blue and should have power anytime the lights are on. The other 2 will show power depending on low or high beam selected.


    Hope that helps.
     
  5. Bill-W

    Bill-W Junior Member

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    Joined:
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    Location:
    Southern NH
    First Name:
    Bill
    Truck Year:
    1986
    Truck Model:
    k20
    Engine Size:
    350
    Thank you very much for your help. I found the problem this afternoon. It was the headlight switch.

    Thanks, Bill
     
    Bextreme04 likes this.

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