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Part Identification...Please

Discussion in 'Tech Discussion' started by Skyfall, May 16, 2021.

  1. Skyfall

    Skyfall Junior Member

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    Location:
    Franklin, VA
    First Name:
    Ryan
    Truck Year:
    1991
    Truck Model:
    r3500 Crew Cab 2WD
    Engine Size:
    350ci
    I was working on my 1991 r3500 (was 2x4, is now 4x4) and saw this item dangling down under the dashboard. It was connected with a blue and black wire in a single black connector. There are other connections on it, but they weren't connected. I tried searching for the part# and had no luck. The yellow part that sticks out slides back and forth like a variable resistor or a position indicator. If this belongs somewhere, I'd like to put it back where it came from.

    Thanks in advance...

    IMG_20210516_120722410.jpg
     
  2. Danderson

    Danderson Full Access Member

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    First Name:
    Doug
    Truck Year:
    1977
    Truck Model:
    K10
    Engine Size:
    350
    Looks like the neutral safety switch. It mounts to the top side of the steering column near the firewall.
     
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  3. AyWoSch Motors

    AyWoSch Motors Full Access Member

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    Truck Year:
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    Truck Model:
    K1500 Sierra Classic
    Engine Size:
    305ci V8
    Yup, neutral safety switch.

    The little plastic clip that's holds it on probably broke. A few zip ties and you'll be good as new. Not really needed though, if you dont want to bother putting it back on.
     
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  4. Skyfall

    Skyfall Junior Member

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    Truck Year:
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    Truck Model:
    r3500 Crew Cab 2WD
    Engine Size:
    350ci
    Thank you both for your responses.
     
  5. Matt69olds

    Matt69olds Full Access Member

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    Truck Year:
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    Truck Model:
    GMC 1/2 ton
    Engine Size:
    455 Olds
    I’m not all that familiar with that model year truck, so the specifics of the wiring are a bit fuzzy. The blue and black wires are a input to the pcm telling it the truck is not in park or neutral. Are those the only wires that were plug in? If so, that suggests to me the purple (start circuit) are connected somewhere under the dash.

    I’m betting the switch either broke off, or is defective. Instead of fixing it the right way by replacing the switch, the previous owner just jumped the starter wires. The engine will probably crank and start in any gear, and no reverse lights.
     
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  6. Skyfall

    Skyfall Junior Member

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    Truck Year:
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    Truck Model:
    r3500 Crew Cab 2WD
    Engine Size:
    350ci
    Thank you. When I get it running again (I have several things disassembled right now), I will check the backup lights, etc. I have the GM service manual and complete schematics for the truck (thanks to eBay) which will be a huge help in tracing out this circuit.
     
  7. Scott91370

    Scott91370 Full Access Member

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    350
    I think starting in 85 that switch is only for reverse lights. The NSS was replaced with a column lock that will not let the key turn if the transmission is not in P or N.
     
  8. Matt69olds

    Matt69olds Full Access Member

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    I believe you are correct, I forgot about the mechanical interlock. Forget trying to start a car that in motion
     
  9. Scott91370

    Scott91370 Full Access Member

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    You can, it just has to be in neutral.
     
  10. Matt69olds

    Matt69olds Full Access Member

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    I did not know that, I thought it had to bring park.
     

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