Wiring tail lights - need help please...

Discussion in '40- & 55-Series Tech' started by xiero, Oct 22, 2005.

  1. xiero

    xiero

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    I'm at my wits end with wiring my tail lights. I've looked at the diagrams in the tech section, but the colors are all different, and I'm starting to pull my hair out after about 5 hours.

    Here's what I have:

    Drivers side colors
    Green
    Green
    Black
    White
    Blue

    Passenger side colors
    Green
    Green
    Yellow
    White
    Blue

    Pardon my ignorance, but in a negative ground system like this, should I have grounds? I tested continuity with a multi-meter and all of the greens have continuity to the chassis with the ignition on, and off.

    I can get the flashers to work, I can get the parking lights to work, I can get the brake lights to work, but not the reverse lights. The caveat - I can't get them to work together (only the flashers, but not parking or brake, only brake, not flashers or parking, only parking, not flashers or brake, etc.).

    Is there a way with my multi-meter to isolate each set of lights, individually, so I can get them to function together.

    Searched to no avail, I'm confident everything works, I just can't find the correct order. Any help definately appreciated.
     
  2. NJFJ40

    NJFJ40

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    I would suggest you definitely run a dedicated ground from the frame to the lights. I did this and it solved my weird electrical/wiring light issues with my tailights. Also, if you have painted frame or POR frame them grind it down to bare metal where you get your ground from.

    I have a schematic I drew up when I figured out my tailight wiring recently. I can find that if you think it will help. Try getting a good ground first and then post back.

    AndrewT
     
  3. spotcruiser

    spotcruiser Geezer SILVER Star

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    The wire colors you listed are at the lights themselves? Are these stock or aftermarket lights? The wiring diagrams for 76 and 78 show red/blue for back-up, white or green/white for stop, green/black for left turn, green/yellow for right turn, green for taillights, and white/black for ground. In the past, I have found taillights with solid colors equivalent to the tracer colors of the harness.

    I would say blue for back-up, green for running lights, white for stop, black for left, and yellow for right. The ground for the fixture is probably a function of the mounting screws (you can add a ground wire if you like).

    Easy to check the function of your lights. Take them to battery, apply battery negative to the fixture case, and apply battery positive to the various wires one by one. Brake and running lights will be the same bulb (dual filament). You can verify the truck wiring with a simple test lamp or voltmeter at the plugs by checking which color wire has power (to ground) under each condition (running, turn, brake, reverse; use a partner here).

    HTH.
    Todd Bull.

     
  4. Pin_Head

    Pin_Head

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    Look for the stripe colors on the wires as indicated above. If there are no stripes, then the wires are aftermarket and you will have to determine which wire does what. Test for voltage on the wires when the turns, brakes, reverse and running lights are turned on. There are L turn, R turn, brakes, backup and running lights.

    The lamp housings are grounded to the bumper or chassis metal and these sometimes go bad. Running a separate ground wire from the metal housing to the frame is a good way to fix this. The reason that you measure continuity of the wires to ground is because there are multiple lights on the circuit and you will see the ground path through the other bulb. This is the same reason that sometimes other lights will light up inappropriately if the housing gound is bad.
     
  5. xiero

    xiero

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    Almost...

    Thanks for all of your help. Here's where I am.

    The wires appear to be aftermarket - no stripes, just solid wires.

    I grounded the case, and using a test light I was able to figure out blinkers, stop light, and backup lights. The parking lights are confusing me. I have 2 leads to connect to the lights (I forgot to mention that the lights are new). On the lights, there are 2 leads available - one on the parking/stop light, and one on the reverse light. Of the 2 available leads from the truck, they both have power, and if I hook one up to the parking light, it works. If I hook the other one up to the available reverse light, it blows the fuse.

    Should the last one go to the marker light? Should I leave one of the leads from the reverse light unhooked? Should it go to the marker and back to the reverse light? (I don't have marker lights, I was going to go without.

    This is really confusing.
     
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