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  •  » 1966 mustang been sitting awhile - electrical problem

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    9/13/2015 6:38 PM  #1

    allmymoney66
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    From: Camden Point, Missouri
    Registered: 11/07/2013
    Posts: 38

    1966 mustang been sitting awhile - electrical problem

    This car has been sitting for a few years while I work on it.  I put in a battery today and bumped the starter.  That part went fine but I pulled out the headlight switch, they came on for a second then heard a short behind the instrument panel and shut it off.  I pulled the instrument panel and couldn't find anything but now have no headlights and no instrument panel lights.  Probably headlight switch shorted out?

     

    9/13/2015 9:33 PM  #2

    lowercasesteve
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    From: Auburn, Ca
    Registered: 4/01/2013
    Posts: 1,289

    Re: 1966 mustang been sitting awhile - electrical problem

    There's a fuse panel inside the driver's side foot well, inside the fender.  One of the fuses probably blew.  I don't know which one, but it should be obvious.  You need to do a continuity check to see where the short is or you will continue to have a problem.  That wiring harness is a bunch of spaghetti.

    Original owner - 351w,T-5, 4whl disks, power R&P
     

    9/14/2015 9:57 AM  #3

    wsinsle
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    From: Belle Vernon, PA
    Registered: 4/01/2013
    Posts: 1,786

    Re: 1966 mustang been sitting awhile - electrical problem

    There is a # 25 wire (Black-orange) hot all the time that feeds the head light switch. Inside the head light switch there is a circuit breaker for protection. Coming off the headlight switch and being feed from the circuit breaker, is the horn wire #460 (yellow) and the rear brake wire #10 (Green-red). Also coming off the headlight switch is a #14 (Black) wire, this goes to the rear park lights and is hot when the head lights or park lights are on. The #11 wire (Black-yellow) goes to the front parking lights via the fire wall plug, and is only hot when the parking lights are on. The last wire from the switch is the head lights #15 (Red-yellow) this goes to the high/low beam switch on the floor. From the high/low beam switch there are 2 wires (Green-black) and (Red-black) that go to the fire wall plug and on to the high and low beam head lights.
         Sounds like one of these wires could be shorted to ground or the circuit breaker in the head light switch just gave up the ghost. Do the horn and brake lights still work with the head lights off? Do the parking lights work?

    If this forum can't fix it, it isn't broke.
     

    9/14/2015 10:11 AM  #4

    BobE
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    From: White Plains, NY
    Registered: 4/04/2013
    Posts: 2,889

    Re: 1966 mustang been sitting awhile - electrical problem

    I agree w/Wsinle's troubelshooting guide, but also suspect the headlight switch may have given up.  As the car sat for some time, the headlight switch contacts could have corroded, you could try operating the switch a number of times (maybe 20) in an attempt to "clean" off the contacts.

    wsinsle wrote:

    There is a # 25 wire (Black-orange) hot all the time that feeds the head light switch. Inside the head light switch there is a circuit breaker for protection. Coming off the headlight switch and being feed from the circuit breaker, is the horn wire #460 (yellow) and the rear brake wire #10 (Green-red). Also coming off the headlight switch is a #14 (Black) wire, this goes to the rear park lights and is hot when the head lights or park lights are on. The #11 wire (Black-yellow) goes to the front parking lights via the fire wall plug, and is only hot when the parking lights are on. The last wire from the switch is the head lights #15 (Red-yellow) this goes to the high/low beam switch on the floor. From the high/low beam switch there are 2 wires (Green-black) and (Red-black) that go to the fire wall plug and on to the high and low beam head lights.
         Sounds like one of these wires could be shorted to ground or the circuit breaker in the head light switch just gave up the ghost. Do the horn and brake lights still work with the head lights off? Do the parking lights work?

     

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    9/14/2015 3:23 PM  #5

    TKOPerformance
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    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,829

    Re: 1966 mustang been sitting awhile - electrical problem

    I'd advise figuring out what went bad, but if it turns out to be the headlight switch I'd highly suggest converting to relay actuation for the headlights.  Modern headlight bulbs draw more continuous duty amps that the bulbs that existed when the cars were built.  This can lead to premature headlight switch failure, which really sucks when it happens at night as you're driving.  The relay actuation moves the high load from the switch to the relay, allowing the switch to live a happy life simply turning the relay on. 

     

    9/15/2015 1:59 PM  #6

    MS
    Forum Originator

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    From: Canyon Lake, Texas
    Registered: 1/24/2013
    Posts: 12,659

    Re: 1966 mustang been sitting awhile - electrical problem

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    9/15/2015 2:46 PM  #7

    allmymoney66
    FYI FORD Member

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    From: Camden Point, Missouri
    Registered: 11/07/2013
    Posts: 38

    Re: 1966 mustang been sitting awhile - electrical problem

    Thanks  gentleman.  I think the headlight switch ended up being okay but I put a new one in anyway.  I  finally found a bad ground near the drivers side headlight.  I had re-done the ground here earlier and it looked good but must have a broken wire somewhere.  I can't get continuity between the headlight plastic  plug and the ground on the firewall.  I have a feeling the headlight plug is corroded.  Will replace both headlight plugs. Dash lights are back on.

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