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Technical Flickering headlights- really dumb question

Discussion in 'The Hokey Ass Message Board' started by Chris, Sep 10, 2020.

  1. Hello all. I have a 1956 Ford F100 that started having an issue with the headlights. After being on a minute or two they start sporadically flicking off and on. Park lights and dash lights are not effected when this happens, only headlights. I am thinking either the headlight switch or high beam switch is faulty (both stock items). I don't have a spare of either, so before I start throwing parts at it, has anyone else had this issue and can point me in the right direction?
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 46,871


    There might be a circuit breaker built into the light switch, that is being overloaded, and doing its job. Check for shorts. Get a new switch. Or add a relay.

    Sent from my Trimline
  3. I used to have a high beam relay that would heat up and make the high beams flicker and shut off after 20min, back to low beam for awhile and they would work again after it cooled off.

    Could be a ground too
    squirrel likes this.
  4. 37 caddy
    Joined: Mar 4, 2010
    Posts: 360

    37 caddy
    from PEI Canada

    I would check all the connections on the lights,see if they are corroded or loose,then check the switch,it might have a loose wire or could be burnt up?.also look at any junction blocks too.I would try the basic stuff first before you start throwing parts at it. Harvey
    squirrel likes this.

  5. partssaloon
    Joined: Jan 28, 2009
    Posts: 455


    Body to frame Grounds. It's probably fighting for a ground an overheating the circuit breaker.
    I've added a larger gauge wire from the headlight socket ground wire to the frame and haven't had a problem since
  6. Good idea, I did not think of that. I will check into it. Thank you!
  7. I have had vehicles do this as well, but this one does it high or low beam
  8. Thanks for the rapid replies. This is a truck that I just put back together, and it did not do it before. So the idea of a ground or short makes a lot of sense...and something I did not think about (an electrician I am not lol). Thanks everyone
    jim snow likes this.
  9. Every time I have had that issue, it was the dimmer switch.
    62SY4 likes this.
  10. 4tford
    Joined: Aug 27, 2005
    Posts: 1,676


    I would look at corrosion first. Clean battery cables and battery post. Sounds like resistance build up that once it warms up from current it flickers.
  11. pirate
    Joined: Jun 29, 2006
    Posts: 524

    from Alabama

    Check the grounds first. Bad grounds seems to be the root cause of automotive electrical issues.
    nochop and olscrounger like this.
  12. Boneyard51
    Joined: Dec 10, 2017
    Posts: 4,351


    If it was a circuit breaker, it would have a somewhat cycle rate, not a random power outage. Now remember I say “ somewhat “ cycle rate.
    Grounds were mentioned, but you want to check the engine or battery to body ground first for light problems, not frame to body. The fact that the parking lights are not effected leads me to believe that ground is ok. But strange things happen with bad grounds!
    OEM light switches are notoriously under size! Just barely big enough to get the job done, so sometimes, especially if a trailer was ever hooked up, the switch could have been over loaded and the contacts burnt. New China switches are even worse!
    These problems can be a booger to locate, but one of the suggestions, here, is your problem.

    Chris likes this.
  13. squirrel
    Joined: Sep 23, 2004
    Posts: 46,871


    Wiggling wires, and seeing what happens, is often a fast way to find problems like this.
    olscrounger, guthriesmith and Chris like this.
  14. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,263

    Atwater Mike

    Right on as usual, Jim... I'd start behind the headlamp switch, (at the wire that goes to the dimmer switch, then where that wire attaches to the dimmer switch itself)
    As the park lights have no problem, ground is POSSIBLY O.K., but park lights don't have the amperage draw headlamps do...
    Boneyard51 likes this.
  15. In late model Ford diagnostics they refer often to performing a “wiggle” test to diagnose electrical issues, as squirrel said, I would start with that

    Sent from my iPhone using H.A.M.B.
  16. jaw22w
    Joined: Mar 2, 2013
    Posts: 1,065

    from Indiana

    The wiggle test solved my last headlight problem. Started wiggling wires and heard a small electrical "snap". Loose spade terminal. Tightened the terminal a little bit, and haven't had anymore problems.
  17. Doublepumper
    Joined: Jun 26, 2016
    Posts: 654


    Don't overlook the headlight connectors. I had a similar problem recently and found the old headlight connector sockets were the problem. New connectors fixed it.
  18. BJR
    Joined: Mar 11, 2005
    Posts: 6,520


    If the headlight switch has a circuit breaker in it, you can sand the points, which has fixed flashing headlights for me in the past. Just like any other points they get burned or corroded after time. Then the resistance goes up, it heats up and breaks the circuit. Cools off and they work again.
    squirrel likes this.
  19. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,263

    Atwater Mike

    Right. Like shovel handles.
  20. Wrench97
    Joined: Jan 29, 2020
    Posts: 146


    Stock headlight switch or upgraded to a later model switch?
    Ford in the late 80's early 90's had this issue with the Tbird/Mustang/Explorer switch.
  21. I had a similar problem and I finally tracked it down to be a faulty headlight switch, the on in my 32 fordoor sedan had fuse on top of the switch and the fiber board on to of the switch had deteriorated and cracked, after removing the switch I had it in my hand and wiggled the wires and the headlights would flicker.

    A new switch corrected my problem. HRP
  22. 37slantback
    Joined: May 31, 2010
    Posts: 396


    Chris I got stopped one time because my headlights were doing as you describe. I had an Olds that had a ground wire from the battery to the body. That wire was nearly corroded through. It made all the difference in the world.
  23. jaracer
    Joined: Oct 4, 2008
    Posts: 498


    I would check it out with a voltmeter. With the negative lead connected to battery negative and the headlights on and flickering, touch the positive lead to the power wire at the headlight socket. It should be within about 0.2 volt of battery voltage. Now touch the positive lead to the ground wire at the headlight socket. Any reading over 0.1 volt means you have a bad ground. If the power lead is lower than battery voltage by over 0.2 volts, you have a power feed problem. You can check the power in and out at the dimmer switch and the power in and out at the headlight switch eliminating one connection/switch at a time. I like to start right at the device with a problem to verify that the problem is either power or ground or even the device itself. That is if it's easy to get to the connections at the device.
    Bugguts and Chris like this.
  24. Thank you, seems pretty strait forward.

    I did check connections and tried running a ground from core support to frame. There is a ground body to engine and engine to frame. This made no difference in the flicker. I pulled the instrument panel out (to gain easy access to light switch) and while flickering wiggled wires but it did not seem to make a difference. I noticed that my high beams are no longer working, so I wonder if this is just a sign that the dimmer switch is going south. Gotta pick kids up from preschool, will keep investigating over the next couple days.

    Thanks everyone, for the help.
  25. jimmy six
    Joined: Mar 21, 2006
    Posts: 7,138

    jimmy six

    If the truck is the same as the car the light switch has the fuse on top in the back, one of the few in the car. High beam switch sound like the culprit. To me both Are pretty cheap if you shop around. I found both for my 56 Victoria at a local auto parts store along with a new ignition switch I could put my guts in so I could use the same key. There are at least 10-20 parts houses specializing in your truck and probably rebox the same Standard brand stuff I bought at the local parts house... just ask.
  26. alchemy
    Joined: Sep 27, 2002
    Posts: 15,868


    The answer to your problem, is to let me bring a trailer and make it my problem. Is a check OK?
  27. Mr48chev
    Joined: Dec 28, 2007
    Posts: 27,530


    My money is on a connection that isn't always connecting somewhere between the headlight switch and the dimmer switch.
  28. 1oldtimer
    Joined: Aug 21, 2003
    Posts: 7,594


    Test light on the back of the circuit breaker and then test light on high beam switch. Follow the power path and see where the flicker is coming from, you can also test grounds with it.
  29. dirt t
    Joined: Mar 20, 2007
    Posts: 4,671

    dirt t
    from Kingman,AZ
    1. HAMB Old Farts' Club

    Please post the fix when you find it.
  30. southcross2631
    Joined: Jan 20, 2013
    Posts: 4,008


    Since the dimmer switch is mounted down on the floor where it is exposed to all of the moisture if the carpets ever get wet and gets wet shoes . I would check there first. Most likely place.

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