MTFCA Forum

I have a friend that wants to switch his T over to 12V, Who sells a reliable 12v starter and alt.

No magic in 12 volts.

If you feel you must!
Admin jeff sells converted to 12V T starters. Its a PITA job. I have done a few also.

A model T generator will produce 12V. It dont know any better.
One must adjust the output to 1/2 for longevity purposes, 4-5 amps is plenty anyway.
That saves a few bucks, keeps a T motor looking like a T motor & avoids some common alt conversion failures.

Will ... It will cost him a hell of a lot less simply to replace battery cables with the proper gauge, clean and shine all electrical connections, use a quality 6 volt battery, and even more important to have the generator working as designed with the current, no pun intended, voltage regulator offered.... If the starter is filthy, cleaning and new carbon brushes, maybe in order along with sealed bearings. ... PLUS... LED bulbs will give a hell of a lot more light with less drain on the battery and generator.

Just look at my website under 12v Starter conversions and you'll find a wealth of info and pics of horror stories of folks jamming 12v into 6v starters. Honestly, I try to talk folks OUT of converting their cars to 12v BEFORE they do it. If it's already done, then I do make 12v converted starters that work well and I must have sold over 100 of them at this point.... They're so popular I keep them in stock at all times. I've sold dozens on T-Bay and mostly through my website.

Unless 6v batteries are wildly expensive or unobtainable, there are zero justifiable reasons to convert a 6v car to 12v. A well maintained 6v car will start and run just as well as a 12v car. Design considerations are different for each, and if properly met, there's no difference.

Keep in mind 6v cars require larger wire for the starter circuit so more power can be delivered to the starter. Who knows what 100 years of owners have done to their cars in the name of "improving" them...
If you want to run 12v accessories on 6v, there are DC-DC boost converters that do the job well. I have one on my car.
Want brighter headlights? Buy 6v LED headlight bulbs from Langs. Game changer.

12v cars require ALL electrical components to be converted to 12v. Yes, you can run your coils on 12v.
The generator will be under a higher load and will need to be adjusted for lower output or you'll reduce its life significantly. A fully rebuilt generator with a rewound armature and new field coils are a good option. Old armatures & field coils develop shorts and fail completely or have reduced output.
The starter will need to be converted or eventually you'll destroy your ring gear AND your bendix.
All light bulbs will need to be replaced.
If you use an 12v alternator (or even a 6v alternator for that matter), the charge circuit wiring MUST be upgraded or you risk a car fire.

This is not an exhaustive list. There are other considerations.

As always, your mileage may vary.
Jeff

Jeff, I have somewhere around 16 years of uninterrupted service of my Larry Becker 12V starter and alternator. I made the switch after 3 failed 6V batteries and two generator failures. As you mentioned I did have to replace all the wiring and lights. I'm all about keeping things as original as possible. Iv changed my 12V battery before coming to Florida and it been in there for 11 years. Of course I guess the difference might be the year round ability to drive the car down here versus putting it up for the winter months. I will try and see if I can find your set up on e bay, What is your e bay handle?

I wonder if your 6V generator and battery troubles weren't related. (?)

TXGOAT2 wrote: ↑

Fri Nov 21, 2025 9:41 am

I wonder if your 6V generator and battery troubles weren't related. (?)

If you don't have a voltage regulator (you still have a basic cutout) and you drive your car often, the battery will ALWAYS be overcharged leading to a failed battery. Overcharging is the #1 killer of batteries. Hence why we devised Model T voltage regulators! The T charging system works well, but there was never a provision for regulating it's output. Modern semiconductors were only first invented in the 1950's.

Jeff

A T generator can be modified to work with an old style voltage regulator. But those are becoming scarce and expensive. A solid state regulator can be expected to extend battery and bulb life. As late as 1936, Packard cars used a 3 brush generator and cutout. Seasonal adjustment of the 3rd brush was recommended. In 1937, the 120 models were equipped with a 2-element voltage regulator while retaining the 3 brush generator. Later cars used a 3 element regulator. I think Chrysler was the first to offer an alternator with an external, solid state regulator about 1963. By the mid-1970s, most alternators has internal solid state regulators. I have a 1981 Dodge W-250 that uses an external solid state regulator. Overcharging wrecks batteries, especially if the electrolyte level is allowed to get low, and overcharging will cause it to get low much oftener that it should.

I have 50 CP headlight bulbs, and if I turn them on, it pulls the ammeter down to zero at road speeds. It peaks at about 10 amps with them off and drops to about 4 amps with the battery charged at road speeds. I'm not clear on whether the generator output is zero when the ammeter indicates zero, or if it is charging at whatever rate the bulbs are consuming power, but not putting any current into the battery. If the latter, it is wasting some engine power and generator brush life, and using up the scarce headlight bulbs when not needed. A regulator would correct these problems and eliminate the need for the driver to use the lights to regulate battery charging.

Grounding the generator will bring output to zero, but using a resistive load to dump power would not. (?)

I converted to 12 volts some 35 years ago when I just couldn't find decent 6 volt batteries and issues with the T generator. . I also installed a late Ford Autolite generator modified to fit the T mount. These aren't being made any longer. When Larry Becker started selling his modified Delco 12 volt starters, I changed over to them in both cars. I have had very good luck with both. The only continuing issue That I have had with 12 volts is the bendix spring. I have broken and deformed many, even with the Becker 12 v starter. I now use Model A bendix springs. They are heavier and handle the 12 volts force much better. I do have to be careful with the two bolts that hold the spring on. I usually have to grind the heads down a bit to clear the cover. If I were to build up another starter T, I most likely would stay with 6 volts.

My 1917 Touring was not built with a starter, generator, battery or electrical system. I decided to install a 12 volt system primarily because 12 volt accessories are readily available, 6 volts not so much. I started out with a rebuilt 6 volt starter but had problems, mostly with the Bendix. Five years ago I installed a WOSP LM256, geared starter designed for the Model T by the legendary Tuckett brothers of England. It is available from Snyders, pricey, (tariffs?) but in my opinion worth the cost. It's geared and the gear engages from the front, so it can be removed without damaging the magneto. I like the fact that it first engages the ring gear and then spins, which means less wear on the ring gear teeth.

I ran a 4 AWG copper cable direct from a compact Odyssey AGM battery under the back seat to the starter, not needing a foot switch because the starter has a built-in solenoid. I've mounted a key switch below the steering column. I ran a wire from the (+) terminal on the starter to a terminal block and distribute power from there. I've installed LED's in the headlights and LEDs in the Kerosene lamps plus a couple of magnetic mounted brake and turn signals. I'm able to keep the battery charged with the output of a Regan "Hot Shot" charger, which converts some of the output of the magneto to DC to charge the battery.

Each of us gets to choose what'll work best on our Model T's. I've been very happy with my choice of 12 volts.

WOSP LM256 Geared Starter

Oldav8tor wrote: ↑

Fri Nov 21, 2025 8:18 pm

Five years ago I installed a WOSP LM256,

It's exactly for this reason (among others) that I perfected my 12volt Model T starter conversions which use stock bendix parts (springs) without causing issues I've and priced them competitively. Thankfully the choice is now purely personal preference.

I for one, dislike seeing these and other modern appendages bolted onto Model T's.... but we live in a free country and to each his own. The good news is these are not destructive additions and can be easily reversed by those who wish to preserve authenticity.

"Necessity is the Mother of Invention" as they say.

Jeff

If I was wealthy, I'd get a nice late model T roadster and put a Ford V8 60 in it.

Jeff,
I understand your point of view, but as you say, to each his own. That said, I suspect others would like to learn more about your starter conversion. I often get asked about running 12 volts by guys rebuilding Model T's and would like to have your starter conversion info to share with them. Ever think of making a pdf info sheet (or have you done so and I've just missed it?)

There have been several discussions about various reasons as well as the the pro's & con's on switching to 12 volts over 6v in the past. To summarize some of the primary reasons mentioned were to boost starter performance, hotter spark, brighter lights and a USB connection for phone or GPS.
NOTE:Alternators require a RPM threshold before they produce power some at 1000RPM no idea what the T versions require
-Stock starter performance is dependent on either battery or starter condition. Enough has been said about the pro's & con's
-Hotter spark has been reported as giving faster coil spark. For 6 volts, it takes approximately 4 milliseconds (ms) for the current to reach the firing point. On 12 volts, it takes about 2 milliseconds (ms) for the current to reach the firing point. This point is dependent on the spark advance being in the perfect position. A camera flash is takes about 1 millisecond.
-Brighter lights. The stock 6v filament headlight bulbs are actually modern tail light bulbs and take about 2-3 amps each. The recommended T generator output is 5 amps not to exceed 10amps. So when the lights are on the battery power is needed to light they up. Not really an issue as there is enough juice to keep the burning four hours. Having said that, there is an issue with over charging the battery with the stock cut-out. This can be remedied by just turning on the lights on/off occasionally or getting a Voltage Regulator (currently available again). Switch to LED Bulbs about 1amp each is easily withing the current generator output and the lights are much much brighter.
-USB connection for cell phone or GPS. Some attachments would need to be made. The simplest & cost effective solution is an external USB power bank One more controversial thought....
Basically the timer is a distributor cap with a rotor. Has anyone tried to use one modern 6v coil instead of 4 buzz coils.

I thought about changing to a 12 volt system on my Model T, until I cleaned all of the cable connections between the battery and the starter, including the starter switch. Now the engine turns over quite well and starts very quickly. I see no reason for 12 volts unless a special accessory requires 12 volts.

I wonder if the geared starter has the same irritating noise that the 1957 Plymouths made.

Art Mirtes

You'd need a modern set of points and condenser and a 4-lobe cam in the timer case to fire the modern coil. I don't think it has room for a high voltage rotor and contacts, and running the high tension plug wires from the timer area would be problematic. A moveable breaker plate would be needed. I think you'd also have enough oil or oil vapor in the timer case to keep the points fouled most of the time. I suppose you could use a distributor from a 9N or 2N Ford tractor adapted to the T timing cover, but you'd likely have to move the fan and fan belt. Not worth the effort, IMO. A master vibrator or I Timer or E Timer would be a much better solution if you just don't like timers. A good set of well-adjusted coils and any of several timer options will give good reliable service with occasional maintenance. A Ford roller timer will work well with good coils and frequent lubrication with a light, non-gumming oil, like MMO. The Ford system operating on the Ford magneto really works well.

Solely for the purpose of being able to charge electronic accessories, it isn’t necessary to convert to 12V. I have found that Verizon’s 12V charger works just fine on 6.5V and above. I mounted a power socket in the bottom of a suction-mounted cup holder and piggy-backed it to the battery terminal on the ignition switch, so there are no irreversible modifications to the car. The charger does draw a small amount if power even when not plugged into an accessory, and I don’t have a battery disconnect, so I unplug the charger when not in use.

Oldav8tor wrote: ↑

Sat Nov 22, 2025 11:05 am

Jeff,
Ever think of making a pdf info sheet (or have you done so and I've just missed it?)

Its all documented in detail on my website.
https://modeltstarters.com/12v-starter-conversions/

Jeff

TRDxB2 wrote: ↑

Sat Nov 22, 2025 12:41 pm

There have been several discussions about various reasons as well as the the pro's & con's on switching to 12 volts over 6v in the past. To summarize some of the primary reasons mentioned were to boost starter performance, hotter spark, brighter lights and a USB connection for phone or GPS.
NOTE:Alternators require a RPM threshold before they produce power some at 1000RPM no idea what the T versions require
-Stock starter performance is dependent on either battery or starter condition. Enough has been said about the pro's & con's
-Hotter spark has been reported as giving faster coil spark. For 6 volts, it takes approximately 4 milliseconds (ms) for the current to reach the firing point. On 12 volts, it takes about 2 milliseconds (ms) for the current to reach the firing point. This point is dependent on the spark advance being in the perfect position. A camera flash is takes about 1 millisecond.
-Brighter lights. The stock 6v filament headlight bulbs are actually modern tail light bulbs and take about 2-3 amps each. The recommended T generator output is 5 amps not to exceed 10amps. So when the lights are on the battery power is needed to light they up. Not really an issue as there is enough juice to keep the burning four hours. Having said that, there is an issue with over charging the battery with the stock cut-out. This can be remedied by just turning on the lights on/off occasionally or getting a Voltage Regulator (currently available again). Switch to LED Bulbs about 1amp each is easily withing the current generator output and the lights are much much brighter.
-USB connection for cell phone or GPS. Some attachments would need to be made. The simplest & cost effective solution is an external USB power bank
power bank.png

One more controversial thought....
Basically the timer is a distributor cap with a rotor. Has anyone tried to use one modern 6v coil instead of 4 buzz coils.

If you have an I-Phone you don't need a USB set up to charge. Put a standard 12 volt power plug in your T and hook up 6volts to it. An I-phone only requires a touch over 5volts to charge. I put one in my 26 to run my I-Phone for my speedometer app as well as XM radio on my bluetooth speaker on occasion. Paul Shinn has a video on U-tube showing and explaining how to do this. It works perfectly.

If your I phone needs to be charged during the day, give the thing a rest! If you use a radio, you miss out on the cadence of a nicely tuned set of coils.
If you can't get anywhere without electronic navigation devices, buy a map. Your T has a happy pace on the road. You don't need a speedo to find it
I drive my T to get away from all this nonsense, not to import it.

Allan from down under.

Allan wrote: ↑

Sat Nov 22, 2025 6:30 pm

If your I phone needs to be charged during the day, give the thing a rest! If you use a radio, you miss out on the cadence of a nicely tuned set of coils.
If you can't get anywhere without electronic navigation devices, buy a map. Your T has a happy pace on the road. You don't need a speedo to find it
I drive my T to get away from all this nonsense, not to import it.

Allan from down under.

Thanks mate. As a retired truck driver with 3.3 million accident free miles under my belt, I believe I am more than qualified to drive my T. I do not need a map as I know most roads in the USA by heart. As far as a happy pace, we have local law enforcement that would love to write a citation for 3 mph over the speed limit. You drive your T the way you want to, and I'll do the same!

You do not need a 12 volt starter, you just need the 0 Gauge battery cables that ford specified in the blue print to get the current to the 6 volt starter.

Most battery cables sold today are 2 Gauge 12 Volt cables that cannot transfer the proper current required.