1947 H light switch wiring

I've got a 1947 H with the four position square sort of light switch. It has a GM alt. conversion done to it already with the 3 wire alt. neg. ground. Also has a distributor. When wired it was wired with a ballast resistor, and a small in line resistor in the alternator small wire, a toggle switch for power on/off, going to a push button starter button to a Ford type starter relay and so on. I'm putting a pair of plain two wire single bulb halogen driving lights on it for headlights, and simialar worklights on the rear but not halogen. There is no light wiring on it currently and had none of the original wiring in it to help. I've looked at Bob M's diagrams and my manuals and been looking everywhere but unable to find anything to tell me what my light box should be wired like. All I can find is the wiring for the generator pos. ground stuff but no help. What I would like to know is first of all what the four positions on the light switch are for. Assuming the far left position is off the next position or #2 right would be lo beam next right or #3 would be hi beam/ and next or #4 is ? The wiring to the ammater appears to be correct as the alternator is charging and starting system working well. Ammeter only reads to + or - 20 amps so alt. buries the needle 99% of the time. Do I need to install a higher amperage gauge? But with the issue at hand also I have only the wiring to the ammeter in the box. I need to know where to install my headlight and rear work light wires from the engine end to the box. The diagrams tell my for example the F terminal on the generator. Well no generator and no clue where that would be now. I have no clue what any of the original wires ever looked like, started from or where they went to. This conversion from 6V pos. ground appears to be a very fine and complete job. All connections were soldered wires heat shrinked and wrapped in loom taped and or zip tied and done very professionally. All the equiptment is new/ such as the battery cables. lugs, battery terminals/ wiring even the screws and lock washers on the light switch are new and protected with dielectric grease. An extremely good job but now the lights. Please shed some light on my low light situation. I'm stuck and haven't even attempted go anywhere yet!

With the original 6 volt generator, the light switch was a combination light switch/generator charge control.

The 4 positions are:
L - Low charge, lights off
H - High charge, lights off
D - High charge, front lights on dim, rear light on bright
H - High charge, all lights on bright.

With a 12 volt conversion, the switch L and H positions serve no purpose - they become simply two alternate "off" positions for the lights.

If memory serves, power supply to the light switch goes to the terminal #1 (bottom of the fuse holder). Rear light should be wired to terminal #2; the front lights to terminal #3.

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Pegging the ammeter is not a problem. You can replace it with a 60-0-60 ammeter if you wish, but it's really not necessary. (The original 20-0-20 ammeter on my Super M has been "abused" like this for 30+ years - it continues to work fine.)

Incidentally if your alternator is operating correctly and the battery is good, the charge rate should taper to 2 - 3 amps a few minutes after the engine was started. However if the ammeter continually remains pegged it means the battery is being overcharged. Best look into it before the battery gets boiled dry!

Hi Bob;

Well I've got a diagram that you had posted on YT here and it shows the headlights would go on the top terminal on the headlight resistor. It also shows where I should hook up the rear light to. It as well shows at the bottom of the diagram where I wish to refer to as a foil wrapped resistor that is labeled as the field resistor has me stumped. Do I need to put a wire on that terminal at all? Currently there is none? Other wise it appears that if I connect the headlights to the top terminal on the headlight resistor and the rear lights to the terminal I would say more in the center, it should be finished. But one more question is can I power the light switch so that the engine must be running to turn on the headlights? Other wise I have power to the headlight switch all the time and if left on could kill the battery. I have my grandson does alot of work with the tractor but he could easily forget to turn the switch off. The battery is brand new so if I trickle charge it to full charge the amp gauge should drop to barely charging if the regulator is in fact working right, is that correct?

>....the field resistor has me stumped. Do I need to put a wire on that terminal at all? Currently there is none?

Right! With an alternator conversion the light switch field resistor is "abandoned in place"; nothing is connected to it.

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>...can I power the light switch so that the engine must be running to turn on the headlights?

Yes. Simply connect the light switch feed wire to the switched (coil) side of the ignition switch.

Caution: To do this the ignition switch must rated for 15 amps MINIMUM - otherwise it can overheat when using the lights!

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> The battery is brand new so if I trickle charge it to full charge the amp gauge should drop to barely charging if the regulator is in fact working right, is that correct?

Correct! With a fully-charged battery, the ammeter will briefly (1 - 2 minutes) show a high charge rate at startup. Charge will then taper to a steady couple of amps or so and stay there.

Bob;

Your a life saver. I really appreciate your help with this. I've been running my brain ragged trying to figure out the issue with the wire from the generator F terminal. I've made my self a complete wiring diagram of how this is wired from nose to tail for my future reference as it has been a challenge. as I stated it's a truely remarkeable job done on the entire project but never imagined that a couple of lights to be wired up could be so rough. Next step was to put in a toggle switch for headlights and one for worklights. I hate cobbled up stuff though. Thanks Again and please keep up the wonderful help and advise!!!!!!!

If you hate cobbled stuff go back to the original stuff and you will have less problems that stuff is 60pluss yrs old and still will work under the same conditions you will need to make yours work.

One item needing mention the dim position works by placing that wire wound resistor in series with the lights. It is powerful (able to dissipate) enough to work with the original headlights. If you put bright lights in it that draw even 20% more than the original lamps (about 7 amps or so) the resisor will glow then blow. One way to manage this is to use relays to control the lights. using the original switch would require your removal of the wire wound resistor to gain access to both the H (full output) terminal, and the D terminal (Dim) so that two different relays can power differing setups of lamps. If only bright is needed, disconnecting the resistor may be needed to avoid the glowing resistor. Jim

Good point Jim!

So long as the 12 volt headlights draw less than 7 amps or so (a pair of "standard" 12 volt seal beams, or 1156 bulbs) the stock resistor will work fine. However if 55 watt halogen lights are installed - about 10 amps for a pair - the resistor could indeed overheat when the headlights are run on the D setting.

If this is the case, a simple solution is to simply disconnect the headlight dimming resistor. The front lights will now burn with the switch only in the B position; the rear light will burn in both D and B.