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Changing a 1950s Willy's 6 volt system to 12 volt

I have a friend that owns a 1953 Willys pickup.
He wants to restore this truck and wants my help to do the work.
We are not even sure the engine runs or if it will need to be rebuilt.

He would like to be able to attach a plow for the winter, just to plow at the farm not
taking it onto the roads much in the winter because of the salt.
Most plow systems are 12 volt and he would like to change the entire truck to 12 volt.

He was told by someone that the 6 volt starter can stay and will work with the 12 volt system.
He was also told that the coil, points, & condenser will also work with the 12 volt system.

He was told that we would have to replace the generator with a 12 volt alternator
Change out all the light bulbs and the electric wiper motor.
And thats about all. Sounds too simple to me!!!

I’m trying to convince him to keep it original as a 6 volt system and add a 12 volt battery under the hood
(there’s plenty of room)
to opperate the 12 volt plow, with a converter to charge the 12 volt battery off the 6 volt system.

What are you pro’s thinking about this.

Those who have a 6 volt system and want a 12 volt system usually go to this for easier starting.

Other than that, if 12 volts is applied to a 6 volt system, you’ll fry every gauge, bulb, and switch in the system.

If you want a 12 volt system, the vehicle has to be rewired.


Theoretically, the wiring should handle 12 volts, because at 12 volts it would be carrying half the current of the 6 volt system. However, if the insulation on the wiring has deteriorated, it might arc to ground when you apply 12 volts.
Every bulb will have to be changed. The heater motor won’t like 12 volts. The coil also will have to be changed. If the vehicle has the original radio, it will have to be reworked for 12 volts. The tubes will have to be changed for 12 volts and the tubes would be expensive if they can even be found. The gasoline gauge will need a resistor to drop the voltage to 6 volts. The oil pressure and temperature probably aren’t electrical on that old Willys. I don’t remember if these vehicles were positive or negative ground.
I do remember that we used to jump start a 6 volt vehicle with a 12 volt vehicle. We made certain to turn off everything and nothing bad seemed to happen. However, we managed to start 6 volt vehicles in cold weather without problems. If the battery is up to snuff and the connections are all clean and tight, it should start readily without problems.

The 12 volt conversion is not that tough…Dropping resistors will be needed for a few of the circuits, heater blower, wiper motor, coil, gas gauge and maybe the temperature gauge. The first 3 items mentioned will need heavy, high wattage wire-wound ceramic resistors. The starter can withstand 12 volts for short cranking periods. Avoid cranking for more than 5-7 seconds at a time…Use an alternator with a built-in regulator, one wire hook-ups are available…As long as the insulation on the wires is good, the wiring will be fine. If you must have a radio, install a modern 12 volt one.

This is not a small project. The devil is in the details. Since you must change all the light bulbs, you may end up changing many of the sockets too to be able to use todays bulbs…While not difficult, a project like this can take a lot of time and cost a considerable amount of money…

There should be kits available for a 6 to 12 volt conversions, especially for a Willy’s. The coil just needs a ballast resistor. And the kit should have resistors for the gauges, blower fan, and other 6 volt accessories. As mentioned, I’d replace the light bulbs with 12 volt. They would be easier to find, anyway.

Around here all a lot of Guys would drop in an 8 volt battery and maybe turn the regulator up(JC Whitney used to carry a 6V S1 alternator) the headlights would probaly be a lot brighter on 8 volts cant imagine the fuel guage would be right either,but the old style batteries it was possible to tap into the lead busbars on the top of the cells and get the correct votage for what you needed(8 volts wont hurt the starter) I wouldnt restore a vehicle and push snow with it,Know what? its probaly possible to run a snow plow off a power steering pump or switch the motors on an electric pump-Kevin

When cars changed from 6 to 12 volts they fed 12 volts to the points to get easier starting when the starter was turning and then had a 6v feed when the key was released to the run position.

This was accomplished by running the wire from the run position through a resistor or through resistance wire. If you run 12 volts to the points all the time you will burn them up.

The change to 12 volts will become necessary sooner than later and with few lights, no radio, no heater and a starter that will operate on 12 volts the switch to a “one wire” alternator makes the switch quite simple while eliminating peripheral problems.

Thank you all for the comments. I knew that it was going to be a bigger deal than what others have told him. But I needed some points from others to have some ammunition when we talk about this today.
Personally I would do an “off chassis” restoration and keep it at a 6 volt system to keep the integrity of a true 1953 willys. And I would not use it to plow snow with.
His brother is a body man and has his own shop at his house for side work. So the big cost for the body work would be reduced pretty nicely, and with the body seperated the proper work can be done to make this a great truck.

Thanks to all.

My son in law has a 50 Chrysler and it starts and runs fine on a 6v Dekka battery that is 6 or 7 years old.

Maybe you could find an old hydraulic plow…They run off what amounts to a P.S. pump. No electrical connections needed so you can continue on with the 6 volt system…

Once you invest the money to restore one of these old vehicles to showroom condition ( lots of money ) you can’t really put it back into everyday farm service because it won’t stay in showroom condition very long…It would make more sense just to buy a 10-15 year old Ford-Chevy-Dodge P/U with a plow and retire the Willys to special events and weekend outings…

And I’m curious about the electric wiper motor. The vacuum operated wipers were commonly used at that time.

I noticed that too. It looks like someone at one point added two completely different wipermotors just above the windshield that they got from two old junkers.

A little update. I talked to him yesterday about the truck and now I realize that he has no intention on turning this into a show quality truck. Or even close to it.
He intends to use this truck 12 months out of the year and even plans to haul heavy loads with it.
That is fine, because the truck was designed to be a workhorse. But it only has a little 4 banger in it and that was enough for what this truck was designed for in 1953. It sounds like he will be working this poor little motor pretty hard… way harder than it was meant to endure in 1953.
He mentioned that He will have a new box fabricated for it (it was converted to a dump with the original box) quote; “and if I need to haul a ton and a half of gravel it will hold up”. Then he mentioned that he wants to make a fake panel with wood boards for the bottom of the box to make it flashy and when he needs to haul all that gravel, firewood, sand, steel scrap etc, etc. , he’ll just pull that panel out.
He does not want to install a hydrolic plow, but a fancy newest model of electric plow that almost hooks itself up. That is why he wants the 12 volt conversion.

He is hard on vehicles as it is. Example; every time I work on one of his friends vehicles, he test drives it and as he’s leaving he says “now I’ll drive it like I stole it”. And he really puts the pedal to the metal. I fix a leaky wheel cylinder and he see’s how fast it will get down the road and tests to be sure that anything that is near breaking, will break. The people wanted the leaky brake fixed not a new transmission.

I’m still leaning on leaving it 6 volts and installing a 12 volt battery to opperate the plow and install a converter to charge the 12 volt battery from the 6 volt system.

Obsolete vehicles with 6 volt generators can be a pain and I found the best and easiest way out was to install an early model Ford alternator with a self exciter regulator. The onl wire connected to it is the charge wire to the battery with a fusible link in it. I have installed those units on many old engines including morphed Jeep 4 cylinders.

If mechanically sound the truck can be usefull if driven within its limits and it is quite limited. The speed might be limited to 45 mph and a great deal of care taken when hauling a load as the ring and pinion and the tapered axles on those were notorious for failing when stressed.

When I was a senior in high school my best friend had a '51 Willys wagon and we used to go to the lake in that thing. Given the gear ratio and lack of power, that thing was screaming at 50 MPH on the open road with very little load and we would get passed by just about everyone.
Hauling heavy loads and operating a plow might be a bit optimistic… :slight_smile:

The Korean War era Willys Jeep had the same engine and transmission as the pickup discussed here. With a 1/4 ton rating that jeep had 5.35 to 1 final drive. If the ratio was stepped down to carry a heavier load I can’t imagine how fast it won’t go. But if operated carefully it should handle a snow plow.

That old military Jeep was capable of just over 55 mph but after pushing one up to that speed and then getting it stopped I never exceeded 45 again.

"When I was a senior in high school my best friend had a '51 Willys wagon and we used to go to the lake in that thing. Given the gear ratio and lack of power, that thing was screaming at 50 MPH on the open road . . . "
@ok4450-- I remember these Willys wagons very well. I do know that the Willys wagons that came out after WW II all came with the Borg-Warner automatic overdrive as standard equipment so that the engine would not be revving too high at normal highway speeds which at the time was about 55 miles per hour.

Re; Vacuum wipers. Owned and driven by me or my family.
41 Stude, 47 Fraser, 52 Plymouth(2), 54 Plymouth, 56 Desoto, 56 Stude, 59,Stude.
None had vacuum wipers.

@Triedaq, the Willys my buddy had was a manual transmission and this was before the 55 MPH speed limit was enacted. We were being outrun by everybody.

The thought of driving one of those old Willys cross-country would drive me insane. The 50 miles one-way to the lake seemed like an eternity with the howling engine, slow speed, rough ride, and noise.

He kept a 12 volt battery in the back to power the 8-track with but that could barely be heard at highway speeds.

Salt will desroy this thing fast and a ton and half of gravel on the back,wont be good on the hiway(75 HP can only be spread so far9the “super Hurricane 6”[flathead wasnt a whole lot more powerful].Doesnt sound like it will be in the land of the running long anyway(He needs a duece and a half or a power wagon)-Kevin