1978 Scout II wiring nightmare

Discussion in 'General IH Tech' started by Tremor, Sep 29, 2020.


  1. Tremor

    Tremor Farmall Cub

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    Hello everyone, after finally getting my scout running right and trying a night drive I have found out I have absolutely 0 interior lights working(including turn signal indicators) the horn is not working, and as well absolutely non of my gauges besides the speedometer and alternator. It looks like the PO had 2 extra lights bolted on the front bumper but other than that it's stock. Does anyone know where I should start besides fuses and bulbs or anything common that causes these all to not work at the same time?

    Thanks,
    Sam
     
  2. stevewillis

    stevewillis Farmall Cub

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    Since your ammeter is working, you are getting power through the bulkhead connector into the cab. If any of your circuits work (exterior lights?), you are further getting power to and through your fuse panel. I would start there. I’m not clear from your question whether you have already checked your fuses or simply know to do so. If your horn and gauge power fuses are good, we can work downstream from there.

    What about other interior circuits? Dome light? Radio? Cigar lighter?
     
  3. Tremor

    Tremor Farmall Cub

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    The only working lights are the headlights, I took a glance at the fuse panel and everything at least visibly looked good and none were blown that I could see, I will have to break out a multimeter and take a look tomorrow and ensure that though. The bulbs all looked recently changed and still good which gives me the feeling it could be a wiring issue but I just want to make sure before I get in over my head. The car has no dome light or wiring for it to be found, no radio and the cigar lighter is missing so I will have to use the multimeter on that one too.
     
  4. stevewillis

    stevewillis Farmall Cub

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    That tells us the following chain of components is functioning: battery -> bulkhead connector -> ammeter -> fuse panel -> headlight fuse -> headlight switch -> bulkhead connector-> headlights -> ground. That’s a good start.

    With so many failed circuits, I would pick one and diagnose from there. Take your parking lights. Since your headlight switch is functioning in at least the headlight position, we know your parking lights are failing at the headlight switch, the bulkhead connector, the bulbs, or the grounds. The headlight switch definitely has power, so everything upstream of it in the chain above is good.

    Your gauge lights are also powered through the headlight switch via the ignition switch (which is working well enough to start the engine). Try rotating the knob; it is a rheostat that dims the gauge lights. It might just be switched off or has a bad spot. If it’s not that, like the parking lights, there are only so many places to test to the gauge light bulbs and grounds.
     
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