Slick 60's

I have a problem with the headlights. I turn them on and all is well for about two minutes. After that they go off for a few seconds then on again. About 30 seconds later they come back on. The problem does not affect the running/marker lights. Is there a relay in the circuit that could be bad? It's a 1965 F100 if that makes any difference for components.

Either corroded contacts in the switch or bad switch. More than likely.

prolly a bad switch. i'll bet moneys.

Blinking headlights is a common problem on slicks. There is a circuit breaker inside the lightswitch that is kicking out . the wiring is a little too light and most everyone has halogen replacement beams that pull more amps. The best fix is to add relays to both the bright and dim circuits,and run a hot wire direct from the battery to the relays,via a circuit breaker. Or better yet ,you can get a kit from LMC that has a new heavier wiring harness and relays for a reasonable price. I just opted to put on relays (I think I used a 40 amp circiut breaker) and havnt had any problem since. I mounted the relays on the left inner fender just behind the radiator support ,where the headlight wires are routed from the firewall. im sure some of the others will post on how they fixed theirs.There has been posts on this subject,but its been some time back.

how to is here

http://fordtruk.com/index41.html

no Chinese wiring for me, made my own harness.

i also can have high and low beam on at the same time.

Thanks guys. Iceman, it says "Do not attempt without beer". Some of you guys are bigger than me. I weigh in at about 175 lbs, so how many beers will I require for optimal light performance?

I'm in this a bit later, but no one has indicated the possibility of bad grounds - a common problem, especially in vehicles in salt country. I had this exact problem occur, and this was the solution.
I would try loosening and then re-tightening bolts that hold the inner and outer fenders to both the core support and the cab in an attempt to clean up the grounding between the two pieces. That may re-establish grounds. And, add some ground wires between the core support, fenders and cab. Make sure the block to ground wire connection is also good. I always have 2, one near the alternator up front to the wiring harness, and one (right now 2) off the back of the engine to the cab.
Check also by the horn relay and regulator. There is a ground wire connection there which may need to be cleaned up.
Headlight relays are a great idea, but if the wiring is in good condition, they may not be necessary (unless you set it up to use both highs and lows at the same time.)
I have been using sealed beam halogens for years, and have had no problems, and I use headlights whenever I am moving as a safety measure.

However, on another topic, the algorithm you have used to calculate certain aspects of your project is woefully inadequate. Although I do not use this type of estimation, still it seems to me you must rework your analysis.

"Beer" and "light" don't go together.

2 common Problems that have nothing to do with all these fancy relays or wiring others have done is plain and simple, Headlight Switch or Dimmer Switch needs to be replaced , if not Bad Ground never have we had a problem lights except what describing and replace with GOOD Quality Parts not cheap xxxx

Wouldn't a bad ground cause the lights to go off and on while moving and parts are bouncing around not making good contact? Maybe I should have added to my information that this happens with the key off, engine NOT running and sitting still in the driveway. This is wgy I was thinking a relay of some sort. If there is one in the switch, which I pulled from a junked out Slick, would this be a good starting place. Also, over tha last few months I have loosened and re tightend some of the fender/core support/cab bolts to clean the grounding contacts. Maybe not enough yet.

Bad grounds can make the breaker kick out. An arcing circuit can actually use more power than a good one, overloading the breaker. Clean up all the grounds and you'll probably be OK.
One thing to check, are the fenders themselves grounded? Half a century or so can do funny things to "solid" mounts! Try running ground wires to the sheet metal parts. Might improve radio reception as well.

Years ago when I had my 74 Explorer, the small lead end cap to my license plate light broke off so I just spliced back the wire loom and made a big nest of copper wire for the bulb to come in contact with. Yes, I just started college so I wasn't too smart... yet.

I went to work at my movie theatre job in the evening and I looked like an ambulance driving to an accident. Every light on the truck was flashing on and off intermittently with everyone getting out of my way.

Figured out real quick what the problem was. I did actually consider keeping it that way but makes it hard to see at night with all that flashing.

Blinking on and off huh??? sounds like a circuit breaker to me.

I usually don't buy LMC junk but I did put their headlight relay kit on my 77. Boy whata difference. The old 77 is brighter at night than my 09 Ranger. I recommend the kit.

while i must definitely agree with the grounding issues
and Banjos statement on beer ("lite beer" actually freezes before regular beer, therefore is not really beer, but beer flavored water)

the relay upgrade allows the full 12v to reach the headlights, especially when the wiring is replaced with 14 ga. wire
voltage drop is always an issue of wiring over longer runs
plug a good power item into a long cheap extension cord and there will be problems.
the lights are definitely brighter with the relays regardless of the flashing issue

doing the relay upgrade will not fix a bad switch or dimmer switch, those should be replaced with quality new parts at the same time if you have the flashing ptoblem.

I'd buy Ice's wiring harness every time over Chinese.

I would've too if I had known he offered one

... if he offered them.

a guy over at fordification was making them. i'm not sure if he still does, but i have one and it is quality. better than the lmc taiwan kit.

Just get a NEW dimmer switch and you'll be in business!!!!!!!

Had the same problem. What is happening is the circuit breaker (yes there are breakers in a slick) kicks out and in as the circuit for the headlights heats up and cools off. Mine turned out to be the switch, the dimmer coil on the back was GONE, allowing full current all the time. Replace the switch. Scared the creeps out of me when it happened the first night out with a "new" truck!