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  1. #1
    FEP Power Member BLK BRD 88's Avatar
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    Default 86 Gt Vert. headlight problems?

    This hasn't happened to ours yet, but a friend in Phx with an 86 GT vert. like ours flipped on the high beams the other day and the headlights went out.
    He says that as long as he is pulling up on the turnsignal lever the high beams will be on, but no low lights, and the highs don't stay on if he releases the lever.

    Have any of you run into this problem? If so, could it be the high low switch, and if so is it that simple fix or no?
    thanks for any help you might offer for me to pass along to him.
    Ron
    Last edited by BLK BRD 88; 04-22-2017 at 12:33 AM.
    I never seem to get the nut that holds the steering wheel fixed

  2. #2
    FEP Super Member erratic50's Avatar
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    Absolutely! Repeatedly. It started a few months after I installed halogen bulbs in mine about 25 years ago.

    Every time it has happened it's been either the headlamp switch or the signal switch that had overheated.

    The main problems are caused by
    1 - the crappy factory connectors used inside the wire plugs.
    2 - poor quality block to body and body to headlight ground
    3 - the wire is too light for carrying the load of halogen bulbs continuously

    The best answer is to fix #1 and #2 then address #3 with an improved circuit design

    You need a 2 relays such as a starter relays.

    Low beam relay:
    1) mount the relays on the core support
    2) wire from the the battery to the relay power input
    3) cut the headlight power for low beam, connect to relay on.
    4) cut and cap the low beam power for the other light
    5) connect from the relay to both low beams

    Do the same with high beams except there are 4 wires for power leads for high.

    Ive driven my 86 Mustang several hundred-thousand miles. This was the final answer to my problem.

  3. #3

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    Reason high beams are staying on when he pulls the switch is that is the flash-to-pass feature
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  4. #4

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    ^^what he said. Working as designed. Flash to Pass indeed.
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  5. #5
    FEP Power Member BLK BRD 88's Avatar
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    Default

    Quote Originally Posted by erratic50 View Post
    Absolutely! Repeatedly. It started a few months after I installed halogen bulbs in mine about 25 years ago.

    Every time it has happened it's been either the headlamp switch or the signal switch that had overheated.

    The main problems are caused by
    1 - the crappy factory connectors used inside the wire plugs.
    2 - poor quality block to body and body to headlight ground
    3 - the wire is too light for carrying the load of halogen bulbs continuously

    The best answer is to fix #1 and #2 then address #3 with an improved circuit design

    You need a 2 relays such as a starter relays.

    Low beam relay:
    1) mount the relays on the core support
    2) wire from the the battery to the relay power input
    3) cut the headlight power for low beam, connect to relay on.
    4) cut and cap the low beam power for the other light
    5) connect from the relay to both low beams

    Do the same with high beams except there are 4 wires for power leads for high.

    Ive driven my 86 Mustang several hundred-thousand miles. This was the final answer to my problem.
    Thanks for the tip erratic50.........I will give him your list of corrections.

    Quote Originally Posted by FoxChassis View Post
    Reason high beams are staying on when he pulls the switch is that is the flash-to-pass feature
    Yeah, but the lights aren't supposed to go dead when you release the lever if the headlight switch is pulled and headlights have been on until he pulled to switch to go to high beams.

    Quote Originally Posted by homer302 View Post
    ^^what he said. Working as designed. Flash to Pass indeed.
    See response to FoxChassis above.
    I never seem to get the nut that holds the steering wheel fixed

  6. #6
    FEP Super Member erratic50's Avatar
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    Default

    The lights work for a while on low or high then they flicker out. You pull the dimmer and flash to pass activates which bypasses the headlamp switch. With this different current path power is there and they come on momentarily until you release the dimmer switch lever.

    you run into these problems due to excessive current demand on the light circuit. high beam circuit (or low beam for that matter) current capacity is wimpy - the lights will go out and stay out until the headlamp switch circuit cools off. It's an overload inside the headlamp switch. It's 50x worse if you have the accessory light group and run the fog lamps constantly. The lights were wired very lightly for the power demands present. Too light for a simple halogen bulb set.

    You can try tightening up the contacts and replacing the headlamp switch. I can guarantee this is only a temporary fix. I've been there 100 times.

    I said to use relays instead because the relay on wire draws almost zero power through the in car switches.


    Another path you could try is LED light bulbs. I haven't messed with them but I know others have.
    Last edited by erratic50; 04-24-2017 at 03:10 AM.

  7. #7

  8. #8

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    Most likely the headlight switch, but could be the multi-switch in the column. Run original wires to turn on relay and pull power from battery. You will never ever need to replace headlight or multi-switch again Because turning on the relay requires the tiniest amount of amperage and neither switch will overheat again.

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