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  1. #1

    Default Murder Mystery ... who killed the headlights at high speeds

    I have been enjoying my TTOP 85 GT for the past few weeks but last night had a scarey moment while at high way speeds on a curvy back road my headlights went out.

    I had clicked on the high beams about 2 min before as I had done many times in the past. I quickly turn the headlight switch from on to off to back on again and everything came back into view again.

    The car has fog lights but they never get power.... not sure what's wrong. My question is what to replace first. None of the mcpart stores in my area stock any of the switches.

    I did remove the headlight switch and it does get warm while the headlights are on but not burning hot. I didnt see any melted connections. The switch appears to have been replaced at some point as it looks spiffy as compared to other components under the dash.


    This is a car I've only had for about 6 months so I'm still fixing things. Your experience is appreciated as we are planning to take this car on the Power Tour 2018 and I don't want to kill my family

  2. #2
    FEP Super Member gr79's Avatar
    Join Date
    Jun 2009
    Location
    SE Michigan
    Posts
    5,141

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    Sealed beams.
    Had similar situation few years ago. Dash lights flickered off/on.
    Replaced HL switch. New BWD brand. Noted connector looked old and little loose.
    Bought new connector pigtail. HL been ok so is part is still in box.

    Check rad support grounds. Both ground points, eyelet connectors.
    Two usually do not go bad at same time. Prob something else.

    In the 80's, used to burn low beams out regularly. One then the other. Every year or less.
    Found and repaired bad butt splice on power wire, repaired years earlier by body shop.
    Location was way back in the harness, under the coolant/washer fluid tank.
    Ok since.

    Fogs
    Had one go out other day. Same one twice.
    Backed off one lens housing mount screw. Light came on (aftermarket Bosch).
    Check bulbs. Keep oil off bulb. Do not handle with bare fingers.
    Power up light independent of car harness. Then backtrack wiring.
    Mine are wired to go off when brights are on.

  3. #3
    FEP Member
    Join Date
    Oct 2017
    Location
    south-central WY
    Posts
    251

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    In my experience with other Ford products of the 80's, the headlight circuit breaker starts tripping out below its rated current, eventually not even carrying the low beam load. On some cars the circuit breaker is part of the headlight switch, which can be very expensive if available. The wiring from battery to oe switch and breaker and back out to the lights also develops more resistance as it ages. I wired the headlights through an external breaker and relay to greatly reduce the current through the switch and oe breaker, which also gives brighter lights.

  4. #4

    Default

    Quote Originally Posted by darkd0r View Post
    In my experience with other Ford products of the 80's, the headlight circuit breaker starts tripping out below its rated current, eventually not even carrying the low beam load. On some cars the circuit breaker is part of the headlight switch, which can be very expensive if available. The wiring from battery to oe switch and breaker and back out to the lights also develops more resistance as it ages. I wired the headlights through an external breaker and relay to greatly reduce the current through the switch and oe breaker, which also gives brighter lights.
    What he said. These cars did that when brand new straight off the showroom.

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