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What are these wires for?

Discussion in 'Gauge, Speedo & Instrumentation' started by Marcos, Aug 14, 2019.

  1. Marcos

    Marcos Full Access Member

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    working on my instrument cluster on my 1980 jimmy. While doing so I find these cut wires in the dash. Trying to figure out what they’re for

    The brown and white wire go to the top of the cluster where the high beam indicator is. All the green wires etc in the red circle are all cut

    46432B33-549B-4B1E-95DE-E10689085FEF.jpeg
     
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  2. Frankenchevy

    Frankenchevy Supporting Member Supporting Member

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    what doesn't work? I'd start there...

    otherwise, I'd start perusing the reference libraries wiring diagrams that hatzie posted up.

    there are some wiring gurus that may know off the top of their head, but they may not see this for a while.
     
  3. Preston

    Preston Full Access Member

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    Agree could be extras from the factory
     
  4. Marcos

    Marcos Full Access Member

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    Everything seems to work fine other than my domelight. Wasn’t sure if the previous owner had cut them or what happened? I’ll try reading the wiring diagrams again. I started there originally but I’ll admit I couldn’t make much sense of it
     
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  5. Boone83K10

    Boone83K10 Full Access Member

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    what cluster do you have? Base? Factory Tach? No Tach? Knowing that will determine what the wires are for.
     
  6. Marcos

    Marcos Full Access Member

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    im not sure if the cluster I have is the original but its a basic cluster with all gauges - No Tach, no clock. Im hoping those wires are just for a tach option. If that's the case im fine with them hanging in there but if they should connect somewhere else im curious to know where
     
  7. Boone83K10

    Boone83K10 Full Access Member

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    the connector inside the red circle. the three wires into the connector and only two wires coming out have to do with the transmission. light green and light blue wires that go out of connector together (2 wires) go to a connector on the transmission and also a low vacuum switch. The light green, light blue and light blue/black stripe go into the rest of cab. Light blue/black goes to 4wd relay. light green to other side of 4wd relay and light blue to brake switch.

    white is almost always a hot for lighting inside of cab/cluster/some sort of light in the truck.
     
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  8. Rusty Nail

    Rusty Nail Whatever! Supporting Member

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    Daannngggg!

    :owned:
     
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  9. Boone83K10

    Boone83K10 Full Access Member

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    White can also be a signal carrier like into brake switch or any switch such as directional indicator or wiper switch or light switch.

    I got my information from my 83 service manual, 80 jimmy may be slightly different but I doubt it. Wire colors could have changed.
     
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  10. Marcos

    Marcos Full Access Member

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    Boone thank you so much for this info. This helps out a lot. I’m guessing the cut end probably passed through the firewall down to the tranny then since the other end is plugged into something up under the dash maybe the relays that you mentioned. This jimmy drivetrain was completely modified prior to me owning it. That might explain why it was cut during its modification.
     
  11. Boone83K10

    Boone83K10 Full Access Member

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    1980 didnt have 700r4 because that came out in 82. So if this wiring is original (and it may have been transplanted, who knows what people have done in these old trucks) then the Jimmy could have had a TH350c. It was like a precursor to the 700r4. It had lockup for 3rd gear.

    Quick way to tell is to see if you have a low vacuum switch right at the 10 o clock position of the brake booster or see if there is a "shadow" of one that use to be there as the paint will look better where the bracket was.
     

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