my 1969 f250 seems to have a faulty headlight switch. not the dimmer switch on the floor. but the pull out switch at lower left of steering wheel. i have had two other old ford pickups with same problem. seems that the switch cant handle the current. after a while the headlight flicker a few times. then go out. i have replaced the floor dimmer switch, but didnt help. this is dangerous indeed. this seems to be a common problem based on my own experience on my other vehicles. heck, even my dads 74 ford 4x4 does the same thing. is there a fix for this ? this problem never does trip any breaker or blow a fuse. just have to give the switch time to cool down then go again. keeping the side floor vent open to help keep the switch cool seems to work. i think that i need a new switch that looks original.

 

New switch can help for awhile. But the only real FIX is to install relays. Plenty of info on this in the tech thread, top this page.

 

High resistance is what does it, these old trucks have lots of corrosion in cables, connectors and grounds and the wire runs are long. Causes switch to heat up and trip breaker.

 

The circuit breaker in the switch does go bad, the one in my F250 was bad when I got it. After replacement it went four years until the next iteration of the truck with no issues.

 

Wrong! Bad information is worse than no information. The reason the headlight switch circuit breaker is tripping is due to excessive amperage draw in the circuit. Unless you measure the current draw and compare it to specs you are simply guessing at the cause. Short of that I would inspect each and every connection from the headlight bulbs to the switch including all grounds.

 

Well you're both right in my opinion. If the connections are clean and bright and tight and grounds are good the problem will go away, although it may need a new switch by now, as it has been roasted inside. Some of the guys here were saying the switches were a problem even when the trucks were new.

My slick uses a generator and have run the Halogen bulbs for years, which is supposed to be a no-go. They worked fine, the current drawn by them compared to stock tungsten isn't that much more if you run the numbers, the wiring can handle it. BUT, any bulb has a sweet spot in terms of a minimum voltage/current that it needs to have, to work right. They won't be any brighter really, if they aren't fed proper.

The relays help get more juice to the headlights and improve brightness. The price has come down a lot.

 

For over 25 yrs had a c/o camper what had like 16 over head clearance lights that the oem switch handled. Then one night heading back to California on a narrow 2 lane desert Rd. my head lights started to flicker and would go out for 15-20 sec. and no place to pull off the Rd. for about 30 miles. Then found a place to stop for the night.

Once back the next day I tracked down the problem at the connecting wire loom plug where it connects to the trucks wiring to the head light wiring right by the left hood hinge wheel well apron. Full of green corrosion. Cleaned with a brass brush then use some electoral grease.

About a yr later was testing all the head & running lights getting ready for a 2 week vacation and all lights were flicking once again. But this time heard the clicking of the light switch relay so replaced with a oem switch and floor H/L beam switch that was about 10-12 yrs ago....

Well sold the camper an have not been out after dark on the road since selling the camper, my eyes our not that good for night driving any more.

But did a night time test drive after installing a 100 amp alternator on it.

Have since installed a 130 apm upgrade plus the dual relays.
Have not night tested this dual relay setup yet though!
Orich

 

My theory:
There is a downward spiral going on here. The original wiring was marginal. Halogen headlights enjoy more voltage and current, which can make them brighter and last longer, but they require that juice. Most replacement headlights are halogen now. They decrease resistance at running 'on' temperatures, and so, place more amp load on the entire circuit.

Meanwhile the old floor-switch gets crunchy, and starts leaking current through both of the headlight circuits, high and low. (You can test the headlight socket that is supposed to be off.) Only the low-beam may light up, but the juice increases, even with a trickle through the high-beam.

These factors put more stress on the ignition switch and/or headlight switch, heating it up, creating more resistance, sometimes tripping the in-switch circuit breaker. After a while, the circuit breaker gets weak, or the switch gives up.

As stated above, grounds, connections, corrosion are all factors, and introduce confusion and differences from time to time.

As an aside, your other circuits get less volts/amps when they need it, and may even make you think you need a new coil, or that you need to delete the 'pink wire'. Missing at light throttle may occur. Flashers may blink strangely. Surges increase. Bad mojo.

2X on upgrading to a "Brighter brights" style of relay system. It works.
The main advantage is you freshen up all the connections, use the right size short wire, and take the whole headlight load off of the headlight-switch and the floor-switch. Afterwards, do aim your headlights properly, because all of a sudden other drivers will think you have high-output headlights. It is not very difficult or expensive. Mine has been working nicely for over ten years.

A 3G alternator upgrade is not required to support this modification. However, it does help at very low engine speeds. But then again, it is pretty awesome to turn on the high-beams on a moonless night, and see the whole mountain in front of you light up! Having enough juice going through the system helps avoid a whole list of other issues.

 

Some basic electrical theory is in desperate need here. It doesn't matter how many "Gs" your alternator has; amperage draw that exceeds the capacity of the circuit breaker will not be affected by more available amperage. If halogen headlights drew significantly more amperage then they wouldn't be direct replacements for original type lamps. Again, unless and until you measure the amperage draw of the circuit, you're guessing at the cause and relying on advice from those that only repeat what their ex-cousin in law heard from some guy down the street with a chevy in the driveway up on cinder blocks.

 

My lights started to go off, and I could hear the circuit breaker click off and on. I have halogen sealed beams. I replaced the 45 yr old headlight switch, with Motorcraft replacement, and rusty dimmer switch, with Standard brand. Haven't had another problem.
My factory wiring is in excellent shape, and all the plugs are tight, and grounds are in place. Works like it should.

 

Remember that these trucks are 45-50 years old with who-knows-what rat's-nest-wiring is under the dash and points beyond with unknown, corroded high resistance connections. You can still put a clamp-on ammeter on the circuits, but you are still dealing old stuff. Unless you are building a Pebble Beach Concours contender which you only trailer around to shows, why fiddle with this stuff, and just upgrade to better stuff like Ford did with later trucks.

 

The engineering in 1969 was the same as it is today. Electrical theory has not changed.

 

I don't think anyone is arguing electrical theory.
The argument seems to me is:
If the conduit at the end is corroded and weak from the barrel of water, tap a source closer to the barrel of water and reroute.
The relay kit rerouted the light switch and runs from the battery thus simplifying the headlight switch to be nothing more than a toggle switch.
We did it on **** truck and it's awesome. We will be doing it to mine as well. He's my son not my ex-cousin.