Technical Flickering headlights- really dumb question

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?

 

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.

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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

 

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

 

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

 

Good idea, I did not think of that. I will check into it. Thank you!

 

I have had vehicles do this as well, but this one does it high or low beam

 

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

 

Every time I have had that issue, it was the dimmer switch.

 

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.

 

Check the grounds first. Bad grounds seems to be the root cause of automotive electrical issues.

 

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.





Bones

 

Wiggling wires, and seeing what happens, is often a fast way to find problems like this.

 

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...

 

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


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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.

 

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.

 

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.

 

Right. Like shovel handles.

 

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.

 

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

 

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.

 

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.

 

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.

 

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.

 

The answer to your problem, is to let me bring a trailer and make it my problem. Is a check OK?

 

My money is on a connection that isn't always connecting somewhere between the headlight switch and the dimmer switch.

 

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.

 

Please post the fix when you find it.

 

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.