Wiring Harness 86 to a 74.

Discussion in 'GM Electrical Tech' started by Scratchy_Joe, Jan 16, 2011.

  1. Scratchy_Joe

    Scratchy_Joe New Member

    I have an 86 GMC. Because of shift tube both ignition components and broken turn signal in the coloum I pick n pulled one from a 74. Starting, shifting is no longer a problem. Now it my lights and turn signals.

    I pull out the lights know. Everything is on. I switch turn left, left side goes dark. Same for right. No break lights or hazzards. No headlights as well.

    ground problem I think. But I am in no way an electrical expert. Other that pulling of the wiring bracket for the colum and trying all the combinations I do not know how to solve this one.

    Thanks In Advance.
  2. dualdj1

    dualdj1 Rockstar 100 Posts

    you need wiring harness diagrams for both years. then you have to trace down which circuits you are working with. This could be a pretty major change with the years you were talking about, if you don't know electrical you probably should've tried to find one from same year, or you may have to take to a shop to get it figured out for you.

    That being said, it sounds like your turn signal relay may also have an issue. But to get that far you need to make sure your wiring harness is patched together correctly, and that means either using a multimeter and testing your wires, or getting the diagrams.
  3. Scratchy_Joe

    Scratchy_Joe New Member

    the diagrams are identical. The switches are in different places but the same wire set up. Well the column does not have the high beam dim switch but that's fine. I now believe the wires in the column are grounding out somewhere.
  4. stephan

    stephan Rockstar 4 Years 5000 Posts

    Did you get the new hazard switch with it? A bad hazard switch or one that is pulled partway on will cause this prob with your turn signals. I doubt your wires are grounding in the column unless you really had to really rip them through there & shaved some of the insulation off.

    No daytime runners in '86 Caddi. You actually used to drive a Ford in those days :) lol....
  5. Taddpole

    Taddpole Member

    I'm pretty sure DRLs started with the 1995 model year. X2 on the four way flasher sw.
  6. Scratchy_Joe

    Scratchy_Joe New Member

    Dear Stephan,

    You were partially right with the hazard switch. The hazard and turn signal assembly was busted and some of the wires were touching the metal piece. A file and some snips alleviated this problem. Thank you sir.
    So after I got the turn signal working. I thought I would handle my dimmer problem. By wiring the hazard switch with the dimmer wires. Really who uses hazard lights anyway. So I did this without checking the fuses. Dimmer is 20a hazard is 15a. needless to say after a few tries I blew the hazard fuse. So I went to the store and got fuses a new turn signal switch and a toggle switch. Now everything works. Lesson learned do not jerri rig wires and switches.
  7. stephan

    stephan Rockstar 4 Years 5000 Posts

    I'm glad you got it fixed Joe. Electrical problems aren't so bad, as long as you "don't let the smoke out of the wires" :)

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