The Stovebolt Site Forums The Shop Area The Electrical Bay Headlights flashing slowly

Folks, I’ve been struggling with my ammeter gauge needle bouncing around a lot and my headlights flashing within about 5 minutes of turning then on

Some basics: 55.1 3100, 235, converted to 12v, generator, 6v coil

I’ve had the gen tested twice with the voltage regulator as it turns out by the Starter/alternator guy that rebuilt the gen years ago. VR was bad so replaced it. I also ran a ground wire from the gen to the VR base. I also checked the headlight ground and they are solid. I put in JonG”s 200,000 hour condenser and replaced and adjusted the points. Also checked the battery and it load tested good. I’ve also polarized the gen, although the gen guy said the gen will hold its polarity for quite awhile after the battery is disconnected.

Anyway, the truck starts fine, runs good and the ammeter needle is relatively stable and essentially centered. When I turn the headlights on the ammeter moves to the discharge side of center and after about 5 minutes the headlights start turning off and on and the ammeter starts bouncing around a lot. I can turn the headlights off and back on and they work ok for a couple minutes then the symptoms start again.

Any help appreciated.

There is a bimetal circuit breaker in the headlight switch instead of a fuse. In case of a short or a high current draw, the lights flash on and off instead of simply going out when a fuse blows. It's a safety factor to allow a driver to get stopped with a little bit of light instead of just flying blind. Almost all of the flashing light problems I've diagnosed and repaired since the early 1960's were caused by a short or a voltage leak to ground in the dimmer switch. It lives in a very hostile environment under the floorboard, where road dirt, rain, and salt try to destroy it, constantly. Halogen type headlights can also cause enough current flow to overload the circuit breaker in an original equipment headlight switch. Putting a set of relays in the headlight circuit and running only the relay energize current through the headlight switch and dimmer is the best long term solution to high current headlight problems.
Jerry

The early headlight switches incorporated a circuit breaker. It could be that the switch is defective.

This is unrelated to the problem with the lights but you indicated that you have a 12 volt system with a 6 volt coil.
A correct 12 volt system should have a ballast resistor and use a 12 volt coil that is stamped with "for use with an external resistor".
A 55 up car or 55.2 truck will have the correct coil.
Fred

Make sure that the nuts on the back of the ammeter are tight. The last guy who worked on my truck neglected to even get one of them finger tight. He is an idiot.
No one but me has ever worked on any of my trucks, which is why I am so confident in my assessment of "the idiot's" skillset...

I had the exact same issue with my ‘52. It turned out to be the switch. Replaced it with a repo original style switch, which solved the problem.

If the problem turns out to be your headlight switch (which is possible but not as likely as your dimmer switch) there is a headlight switch repair tutorial I wrote sometime around a year or two ago. Not in tech tips, sadly but it is searchable. Good luck.