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Technical Wiring Gremlins- headlights- help please

Discussion in 'The Hokey Ass Message Board' started by Roothawg, Aug 12, 2022.

  1. Roothawg
    Joined: Mar 14, 2001
    Posts: 24,522

    Roothawg
    Member

    I have a buddy that just stopped by the house in a car he just restored. It's a family heirloom.

    Background:

    The car is an OT Ford, but the headlight problem should be universal. His wife got this car back in 1978 for a high school ride. Her dad had this very same problem, so he bypassed the headlight power and used a hokey toggle switch. My buddy couldn't stand the idea, so he wired it back the way it was supposed to be. New headlight switch, new headlight bulbs, new dimmer switch.


    I saw him coming down the road with his lights strobing like they were on a timer. I thought he was wanting to get my attention that the car was back on the road, until he got out and they kept doing it. He lives a mile from me. From the time he leaves his house until he gets to my drive it's fine, then it starts flashing. The same thing happened when I followed him home.

    Troubleshooting:

    It only pulsates the headlights. The tail lights, brake lights and turn signals all work when this is happening. If you drop it back to park lights, no pulsing.

    My thoughts are that maybe there is a relay somewhere getting hot and chattering? Like I said he has new headlight switch, new headlight bulbs, new dimmer switch. The only thing original is the wiring.

    His father-in-law has wondered for years what this gremlin is. It would be nice to finally ease his mind.
     
  2. The circuit breaker in the headlight switch is probably pulsating on and off.

    This happened on my rod when I switched to halogen bulbs as they drew more amps than the switch was able to handle.

    Sound familiar? If so, there is a fix.
     
  3. 59Apachegail
    Joined: Apr 30, 2011
    Posts: 1,504

    59Apachegail
    Member
    from New York

    I cooked a wiring harness with halos. I wired in fogs that were halogen and my dash started smoking. Scared the piss out of me, I was at the gas station. I added in a relay.
     
    Roothawg likes this.
  4. Fabulous50's
    Joined: Nov 18, 2017
    Posts: 513

    Fabulous50's
    Member
    from Maine

    The correct thing to do is use relays on the headlights IMHO.

    One relay for low beam, and one for high beams. Wire it from a good power source, and fuse them at 20A each. One fuse for low and one for high. The stock switch, wires, dimmer etc all just have the small load of the relay coil.

    We can help with wiring them in if you need it.

    I agree it's likely a circuit breaker which has lost its bimetalic spring and instead of snapping is now rapidly pulsing. The relays will fix it!
     
    Roothawg, 47chevycoupe and Johnny Gee like this.

  5. Or try a new circuit breaker....
     
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  6. dalesnyder
    Joined: Feb 6, 2008
    Posts: 609

    dalesnyder
    Member

    This is pretty common when the headlight switch starts going bad,
    To make sure you can drop the headlight switch and check the plastic wiring connector for signs of overheating, they will get really deformed.
     
  7. Typically Fords of that era were wired with power directly from the fuse panel to the switch, which had separate internal contacts for headlights, parking lights, tail lights, and dash lights. Headlight power out of the switch went to the dimmer, with a separate lead going back to the high beam indicator. Does that pulse also? If so, probably a faulty dimmer switch. If not, could be a wiring issue going out to the headlights. Each headlight side has its own ground, so that it most likely not it. A factory wiring diagram would help.
     
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  8. I also say dimmer switch. They are easy enough to swap out.
     
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  9. Root cause analysis.
    If it is a circuit breaker cycling, then what's causing that? o_O
    You said the components had been replaced so I'd look for shorts/broken insulation in the headlight wiring.
     
    tommyd, 427 sleeper, deucemac and 3 others like this.
  10. greybeard360
    Joined: Feb 28, 2008
    Posts: 2,074

    greybeard360
    Member

    I have never seen the circuit breaker reset fast enough to cause headlights to strobe. Are the actually going completely off then on or are they flickering dim to bright? I would monitor charging voltage when it happens. It could be an alternator problem. My gf vw headlights do that at times. It has the original 79 alternator and it is a little goofy but still keeps the battery charged.
     
    Algoma56 likes this.
  11. winduptoy
    Joined: Feb 19, 2013
    Posts: 3,319

    winduptoy
    ALLIANCE MEMBER

    Some OEM headlight switches have the circuit breaker in the switch. They can be problematic and if you are hunting for an external wired breaker, drive you nuts. Best to check the current draw and see if it exceeds the amperage draw and maybe an easy way is to unplug one headlight and see if it happens with just one on the circuit.
    My thoughts...good luck
    It's the ground...it almost always is....
     
    Boneyard51 likes this.
  12. WAIT A SEC! They worked with a TOGGLE switch, but flicker/blink with the original AND replacement switch? So, from toggle onward, must be OK. Presumably this would include the dimmer. So short/overload, if one exists, is near the switch. OR, some accessory is added into the light circuit that overloads the breaker.
    That would be a fun one to chase.

    Ben
     
    427 sleeper likes this.
  13. Mr48chev
    Joined: Dec 28, 2007
    Posts: 33,861

    Mr48chev
    ALLIANCE MEMBER

    That car still comes from the age when most cars didn't come with halogens from the factory and if it has halogens even the H models of the oem lights off the parts house shelf the load may be more than the switch can handle.

    It isn't hard to wire in a pair of relays and that is what I would start with.
    [​IMG]
     
  14. A bit more information is in order.... '50s to early '90s Ford OEM light switches have a 15 amp internal circuit breaker that protects the headlight circuit. The same type switch is used on both 2 and 4 headlight models although there are minor differences as the cars get newer. Designed to carry the current of the OEM lights, if the vehicle has 2 lights the switch can carry the current of any 'legal' upgrade light, typically a 55W low, 60W high. That's not the case with 4 light cars. The OEM lights are 50W low, but only 35W high and any upgrade light over 35W on high will overload the breaker. So do check the wattage on the replacement lights. Putting the upgraded high beams through a separate circuit switched by a relay is the usual fix. You only need to separate the inner, high-beam-only lights onto their own circuit, the outer low-high lights can stay on the switch. A 15 amp circuit will be enough for this.

    The 'strobing' is not typical behavior when overloaded. Generally, what happens initially is the lights will go out and after a brief cooling off period will come back on. If the overload persists, the 'off' interval will increase and the 'on' time will decrease. The strobing strongly suggests a defective light switch which is all too common with aftermarket light switches. Investing in an OEM switch would be my recommendation.

    A few other things to check. Starting in the mid-'60s, Ford supplied TWO circuits to the light switch; one for the headlights only, and one for all other lighting. Make sure that all power connections to the switch on the headlight side are good. This type switch can be identified by a lack of fuses on the switch. The early switch type has the tail and instrument lights fuses on the switch and a single power feed, the dual-feed switch will have those fuses in the fuse panel. Check for shorts to ground. Pull all the headlights, disconnect the switch, and check each hot wire to ground. Make sure you perform this test with the dimmer switch in each position. Anything less than an 'open' reading is a problem. Also check the wire resistance between the headlight sockets and the switch plug, again checking with the dimmer switch in each position. Anything above a few tenths of an Ohm is bad, you'll need to find the poor connection. Make sure the headlight grounds are good, again anything over a tenth or two of an Ohm is bad.
     
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  15. Roothawg
    Joined: Mar 14, 2001
    Posts: 24,522

    Roothawg
    Member

    Keep in mind guys, this happened back in 78 long before halogens were out. Also, he replaced the light switch, dimmer switch and bulbs.

    I will ask if they are halogens.

    The headlights do go completely dark, but all the other lights stay on at full power.

    It's a 1972 M car if that helps....

    Thanks for the info so far. You guys rule.
     
    Last edited: Aug 13, 2022
    Just Gary likes this.
  16. hemihotrod66
    Joined: May 5, 2019
    Posts: 968

    hemihotrod66
    Member

    Always check the grounds in the system...
     
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  17. Gray-market Euro-spec Halogens were around in the late '60s, but weren't common and/or legal in most places. I bought my first pair in '71...
     
  18. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,440

    Boneyard51
    Member

    Disconnect one headlight and see if it continues! If this stops the problem you have is a current issue!






    Bones
     
    Last edited: Aug 13, 2022
  19. Doublepumper
    Joined: Jun 26, 2016
    Posts: 1,534

    Doublepumper
    Member
    from WA-OR, USA

    Interesting...wonder if there's an issue with the gen./alt. or voltage regulator. It may be something happening all the time, but is only noticeable through the headlights, or the added current of the headlights may be causing one of them to act up.
     
    Roothawg likes this.
  20. Just a guess without testing, you’re going to need to locate a good nos or nors headlight/dimmer switch AND install a headlight relay. But first check power output, grounds and resistance…..could have higher then normal resistance in a wire or connectors.
     
  21. I had a '71 F100 that did the exact same thing. Got a new OEM light switch from the Ford dealer(this was back in the 80's) and it worked fine after that. Not sure why the switch failed though....
     
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  22. Roothawg
    Joined: Mar 14, 2001
    Posts: 24,522

    Roothawg
    Member

    I'll send him a link to this thread. Thanks guys.
     
  23. jaracer
    Joined: Oct 4, 2008
    Posts: 2,419

    jaracer
    Member

    I don't have any idea what could cause this, but I'd really like to troubleshoot the problem.
     
    firstinsteele and Roothawg like this.
  24. sunbeam
    Joined: Oct 22, 2010
    Posts: 6,213

    sunbeam
    Member

    Does it do it sitting still?
     
  25. Roothawg
    Joined: Mar 14, 2001
    Posts: 24,522

    Roothawg
    Member

    Yes.
     
  26. I have had bad bulbs in turn signals do all sorts of funky stuff before. I agree, disconnect 1 headlight at a time and see what happens.
     
  27. jaracer
    Joined: Oct 4, 2008
    Posts: 2,419

    jaracer
    Member

    Does it make any difference if the engine is running or not? Is the power to the headlight switch the same power that was attached to the toggle switch? Are all the female spade terminals in the switch connector tight? You can see by taking a male spade terminal and trying it in each of the female terminals on the connector.
     
    Roothawg likes this.
  28. nochop
    Joined: Nov 13, 2005
    Posts: 3,818

    nochop
    Member
    from norcal

    Re check the grounds?
     
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  29. cshades
    Joined: Sep 2, 2011
    Posts: 554

    cshades
    Member
    from wi

    had a early 60s chevy truck in for this problem. had the 4 head light system and pulled enough current to strobe the lights added a relay and all was well. it did have halogens added
     
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  30. Roothawg
    Joined: Mar 14, 2001
    Posts: 24,522

    Roothawg
    Member

    He’s following along on the thread. I’ll probably see him over the weekend. We will see if we have made any progress.
     
    Johnny Gee likes this.

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