Technical Headlight switch and wiring

On a road trip early yesterday morning and all the lights died. Pulled into a parking lot, checked the fuses and sure enough, headlight fuse was blown. Replaced the fuse, no headlights, but we had brake and turn lights. While pulling the switch on, the rod came all the way out of the switch body. I'm pretty sure that the switch is the original 6v, but the electrical system is now 12v. Another issue is the way the lights were wired. Just turning the ignition switch to "On" and the lights won't work. The engine has to be running for the lights to work. Currently, none of the lights are working, so I'm pretty sure another fuse is blown.

I can get a Universal Echlin 12v switch from NAPA, no problem. I'm just wondering how the wiring got screwed up like it is. I see a long process of elimination to get it right. Anyone got any ideas?

 

It would really help to know what car you are talking about, and is it stock wiring or aftermarket kit.

 

'48 Ford coupe. Pretty sure it's the original 6v headlight switch. Aftermarket wiring kit with no markings. Already ordered a 12v universal switch. Today, the plan is to pull the ground from the battery, remove the headlight switch and tie each group of wires from each terminal on the switch into separate bundles, then trace each wire in a bundle until I can find where they are actually going. I have no intention of just blowing all the wiring apart and guessing where it all was originally. This car is going on a road trip to West Texas next week and I don't want to be on the side of the road checking wiring.

 

12V is less amperage on 6V wiring so that is not an issue. Dennis Carpenter shows to have an NOS switch for that application for $75. Strange that the engine has to be running and not just ignition on, I don't see how that can happen easily. I think I would start by chasing the power wire to the switch and see where it goes. Maybe it goes to the voltage regulator somehow and that is why it only works when running?

 

I had problems with the lights in my '47 when I got it. It had the original light switch and dimmer switch. I replaced the headlight switch with one from an 80's Ford pickup from Pick and Pull. The new switch has a much larger dimmer rheostat, and my marker lights are on with the headlights.
Have you looked at your dimmer switch? The wire from your light switch goes directly there, then on to the lamps.
I also installed relays near the headlights to assure that there is full alternator voltage to the lamps.
If your system was working properly until now, it's unlikely that wires got crossed.
Here's a typical wiring diagram from early Fords. It's pretty simple to follow.
P.S. - Make sure your grounds are well connected.

 

Something special in west TX Alan? Where?

Ben

 

Girl I graduated high school with in Oklahoma, back in the days before calculators, computers and cell phones. Never went out with her once, but we've managed to stay in touch over the years. She's been pushing me to get this car done and drive it out to her place.

 

Thanks for that. I'm having a problem with why the light wiring is wired into the ignition switch. Nothing comes on unless the engine is running.

 

OKAY.
Enjoy.

Ben

 

Thanks, I'll check that also. I'm finding lots of wires that just run off into nothing. Pretty sure there was no use of a schematic.

 

My game plan is to run 2-lanes all the way. I want to stop at @Roothawg 's new shop in Newcastle, OK and Wichita Falls isn't too far out of route from Weatherford.

 

Odd the lights are wired to the ignition.
But doesn’t that car have a circuit breaker for the headlights?
I recall a little “box” with one on a ‘42 PU I used to have. At least I think that’s what it was.

 

Perhaps the person who did the wiring didn't want the lights on unless the ignition is on, so you don't forget to turn off your lights. That's common in European cars. The headlights on my 72 BMW go off if you turn off the engine. It was the same on a Saab I had in the 1980's.

 

Typically headlights on most US cars are wire directly to a battery source, not through the ignition switch. Having it go through the ignition switch puts quite a load on the switch.

I just re-read your post. You said the engine has to be running for the lights to work. Are they running the lights off the armature terminal on the generator? That's pretty strange, but it would work. The cut-out relay in the voltage regulator disconnects the generator whenever output voltage is less than battery voltage. So with the ignition on, but the engine not running, you wouldn't have any headlights.

 

Coffee is on me!

Ben

 

Haven't been able to get into the wiring yet. My new headlight switch comes tomorrow, so I'll start checking then to see where power for the lights comes from. From what I've seen, though, there are an awful lot of wires running to the ignition switch., which seems odd because every circuit is labeled on the fuse block. One of the previous owners eliminated the starter button, so everything seems to run off the key switch, which is also the starter switch. I love wiring, especially when someone else does it with no explanation of why it was done that way

 

If the switch you are getting has a fuse on it do not use it. Loose fuse connection will over heat the fuse and it will pop, at least in my case. YRMV.

 

Easy, get a switch you like, wire it up how you like (you can run a new wire for constant power). Pull the old switch down, draw a diagram of it as is, start testing wires to see where they go and then hook them to new switch. You might need to modify stuff like adding a relay or circuit breaker to make it right if the existing setup is wrong.

I like to use a power probe to test if there's no sensitive circuitry, it has an internal circuit breaker.

Basic:
https://powerprobe.com/en/ppbasic/

With display:
https://powerprobe.com/en/power-probe-pp3-circuit-tester/

 

I'm not a fan of universal headlight switches unless you cannot get an oem style. 1. and important every time you look at it the knob will not match. 2. they usually leave someting lacking as far as connecting the wires.
As far as the lights only working when the ignition is on, who ever wired it probably wanted it so that the lights went off when they shut the key off.
If the car is running Halogens they can draw a lot more amps than non halogens and in my experience are hard on old switches. A pair of relays for the headlights cures that and puts a lot less stress on switches.

 

That's where a lathe comes in; you make your knobs all match.

 

Don't know, I haven't gotten that far.

 

No e if which explains why they only work when the car is running, yet not when the key is on. That’s the real mystery, that’s not easy to do.

 

Sometimes it easier just to disconnect all the previous guys wiring terminations and start over with your own approach to directing those electrons
I say that, I just straightened one out where multiple color wires had been spliced together to make its journey from the front of the car to the back.....fun tracing
good luck there sparkie and may your headlamps continuously light the way

 

If it has, or had, a circuit breaker at some time, I haven't seen it. Near as I can tell, when the wiring kit, by an unknown manufacturer, was installed, I think that whatever wire that happened to be closest was the one that got hooked up for a specific use. I'm getting ready to remove the 9,000 or so little, tiny zip ties that are holding everything in place. In a few minutes, the underside of the dash is going to resemble spilled multi-color spaghetti.

 

You can warm the shaft and pull the knob off. JB the shaft to the other knob. AAW sends new light and look alike knob. I put the real knob on their shaft.

 

Sounds like fun.
There shouldn’t be too many circuits in the car.
Are you going to replace the mess you have or work with it?

 

And, I just re-read yours. This is a 12v alternator one-wire system. The

(#1) Got rid of the shut-off switch. (#2) Got rid of the extra 10 or 12 inches of spliced odd-ball wire and put a terminal eye with shrink tube directly on the red wire. May not be any better, but I feel better for it. (#3) There is a wire running from the ignition side of the coil back into the dash which I haven't been able to trace yet. Seems to me, that ignition wire should run to the ignition lug on the starter solenoid. As I recall, we would run a temporary jumper from the ignition lug directly to the ignition side of the coil to try to start an engine on the ground.

 

#2 looks like a fusible link and depending on what solenoid it is, the "I" usually is a 12v kick up for a points cars (12v to coil while cranking).

The wires to jump to crank the engine would be a jumper between the side lug battery wire and the "S" terminal

 

I don't know if this is helpful, but:

• The stock switch seems to have an internal thermal static relay. When it gets too hot (current overdraw) the
  thermal static relay. (flat piece) opens and no lights.
• It appears from the schematic that the lights get voltage for two source/paths depending on operation:
  - Ammeter/battery when the ignition is off and through the thermal static relay
  - Ammeter/regulator when the engine is running
  It is a little hard to tell without actual internal schematic of the switch if this is really true, but
  it would be my guess from looking at the schematic.

You may be chasing two problems:

1. Bad switch (by the way, on an older Chevy, you remove the switch rod by pressing a small button on the
   underneath of the switch and sliding out the rod with the knob. Then remove the switch body).
2. The source of the current draw that caused the thermal static relay to open (often once open, they are deformed and don't work again.

Not sure if this helpful, but it may spur some additional thoughts, good luck (love 48 Fords).
don

 

Update: The '48 has lights separate from the ignition again. I went through and started removing a number of wires that were tied into terminals and ran off to nowhere, and a few that were just hanging out under the dash not attached to anything. One of the terminals on the key starter switch had multiple wires going to the dash lights and somewhere else that I haven't found yet, so I removed anything on the switch that had nothing to do with the starter or ignition. Have to run to town and pick up some blinker fluid, turn signals don't want to work.

P.S.: I've decided that I either need to lose some weight or remove the front seat if I'm going to work under the dash again .