I have a chance to buy a T having a 12 volt system. Am not familiar with such a conversion and thought to ask about it. It also has a distributor and a single coil. What changes are made to accommodate the 12 volts? Different generator, starter, wiring, lamp bulbs, horn, etc. What is the advantage in changing to 12 volts?
Thank you for an education. It will be much appreciated.
Allegedly 12 volt batteries are easier to find, but I find the six volt ones at any farm supply. You can run modern accessories on 12 volts, but you can also run them on six with an inexpensive inverter. A properly maintained T will start equally well on six or twelve volts. I've read that the coils fire better on twelve volts, but if you're running on MAG the battery is irrelevant. I believe you do need twelve volts if you install air conditioning. The disadvantage is that if the coil goes bad the car is dead, while with four coils you can limp along on three for awhile if you have to.
Steve, your are preaching to the choir.
Twelve volt batteries are easier to find and at Costco, cheaper, you can’t deny that.
Most accessories run on twelve volts and don’t need an inverted.
With 12 volts you can get a reliable inexpensive alternator and if done correctly, all charging problems go away.
The T starter can be rebuilt to run reliably on twelve volts and once set up, starting is very reliable.
As for a distributor, use a Bosch coil, keep away from Chrysler products and Bosch products rarely fail. The coil on my Bug lasted from 1967 until I sold the car in 2016, 39 years.
Now should you do a conversion, that’s a different question. My coupe is still six volt and runs just fine. My 14 Touring was set up for my daughter with two small kids at the time and I wanted close to 100% reliability, so I went for a properly engineered twelve volt system. JMHO.
What is Costco?
Jay I am a NOVICE T guy, but been in electronic and electrical work for many years, The short answer is the lamp bulbs and generator or alternator will need to be 12 volts, the starter should be 12 volt as well but many conversions use the 6 volt starter on 12 volts, which while it works and greatly increases cranking speed it is hard on the starter components mainly as I understand it the ring gear and Bendix not to mention doubling the voltage on the 100 year old starter winding, which by all indication 6 volt starters seems to work well on 12 volts for years in many cars but is not ideal, some recommend using 12 volt starter cable which uses smaller gauge wire than factory heavy gauge 6 volt cable and has a voltage drop / Resistance that tends to limit surge current when the high current 6 volt starter is engaged lowering the strain on the Bendix and ring gear, some have had good luck others complain of short life for their Bendix and tearing up ring gears, I don't know but there are many folks on this forum that do.12 volt model T starters are available some are new reduction gear design, others have their original 6 volt starters rewound for 12 volts. My 26 Touring uses 12 volts on a 6 volt starter and it spins like the devil when I hit the starter, the key seems to be short bursts of the starter don't stand on it if it doesn't start right away. The wiring harness seems to be the same for both 6 & 12 volt systems, and the coil needs to be one that functions on 12 volts, some are 12 volt coils others 6 volt with or without a series dropping resistor. as to the advantages of 12 volts over 6 volts if any depends on who answers the question, 12 volt lamps draw about half as much current as 6 volt lamps, for the same wattage lamp, lower current means less problems with marginal wiring connections and perhaps brighter lights, along with a much wider selection of 12 volt replacement lamps as opposed to 6 volt, Biggest advantage would seem to me to be faster cranking speed which if Your T is running properly should not be a issue, except perhaps in very cold weather. Most car manufactures switched over to 12 volt electrical systems in the fifties, and alternators in the sixties to provide more power for all the accessories, Radios, heaters, A/c ect while reducing wiring size in wiring harnesses, 12 volt batteries have twice as many cells as a 6 volt battery and about double the power available for the same size battery, many military vehicles and air craft use 28 volts to reduce wire size and weight while reducing power loss in long cable runs. As I said I am a NOVICE T Guy and not a expert on them by any means, but thought I would try to answer the electrical aspects of your question, which is not to be considered the Gospel on the subject, The old T guys know much better than I will ever know what works for them and what doesn't,
Costco is like Sam's Club. You pay a membership fee and then you can buy all the GREAT products they want you to buy and the price is usually a good price, if you really need it.
Stuff like fifty pound boxes of rice Krispies. 20 pounds of M&M's. You get the drift.
The top 5 advantages of a 12 volt system:
There's nothing wrong with 6 volts. In my opinion, what usually happens is someone's 90 year old electrical system is in shambles. They wont part with the money to put it back like it was. They buy a 12 volt battery which turns their raggedy worn out 6v starter at mach speed. Then they buy a cheap alternator to charge the new battery, vowing to keep the hood closed at car shows. A couple of bulbs and they're in business. And in the words of Ron Patterson, they declare victory. If they had a good starter and a good generator and good connections on good wiring, their 6v system would have been just as reliable. More so if you consider what is happening to their bendix every time that thing slams against the flywheel.
Jay: the actual advantages can possibly be in the mind of the person that converts it. That may sound crass but it's true. If the 6 vt. is there get it working properly and it does the job. Your's was converted for whatever reason so run with it. Properly done it works too there's just no sold reason to spend the $ to do it.
There is nothing wrong with a 12 volt Model T. Beauty is in the eye of the beholder.
Here are my experiences:
Carry an extra Bosch coil and a set of points and drive the pants off it !
Dave, I was being facetious. I know both Costco and Sam's club, and there are vast swaths of the country (like here) that have neither. But we do have farm supply stores where six volt batteries are readily available. The local Orscheln store has six volt Country Tuff batteries for $80. The Wal-Mart next door sells the twelve volt EverStart equivalent size for $93.76.
Jay, I have two T's that are 12v. They came that way so I just went with it. Works just fine. I also have a TT that came with 6v, I went with that. Works just fine. One 12v car uses T coils, I carry spare timer, coils and have had to use them a time or two. The other 12v car has a distributor, I carry points, condenser, coil and rotor. It's not a big deal. I also carry a bendix and bolt in every tool box. These things are known to break, be prepared. The biggest advantage to 12v is lights to the rear. On 70 mph roads you want to be seen.
For me, using 12 volts has nothing to do with starting or running. I easily can use many devices including a small air compressor without worrying about the voltage. The biggest advantage to me, with 5 cars, is that I just have two batteries and can switch them betwixt and between without worrying. While I have never had any starter component issue running on 12V, I now put an old starter spring in the starter circuit and it reduces the voltage to 6 volts. Remember many of these 6V cars were run in the winter, and the cold stiff engines created many starter component problems. Today, with better oils and generally warmer usage 12V into a 6V starter is less of an issue. Do what fits you and enjoy your cars!
Been using 12V for 30 years. Works for me. Jerry.
Here is my advice (for what it might be worth). If it is already 12 volts and has a distributor and light bulbs for 12 volts Leave it as is. The T generator will actually charge a 12 volt battery but is marginal. If you have an alternator leave it alone. If a generator and it still works, leave it until it breaks down then replace with alternator. The starter is the one weak point. The starter will work with 12 volts, but will spin very fast which slams the bendix into the flywheel. If you always remember to pull the parking brake on and always remember to retard the spark before starting, you might get by for a long time with a regular T starter. If just once you forget to pull on the brake or to retard the spark, your starter will slam into the flywheel and very likely break either or both the bendix and flywheel gear. The original starter can be rewired for 12 volts and maybe yours has been, but maybe not.
If you ever decide you want the true T experience you can switch to magneto and coils. Usually a distributor is placed when the magneto stops working and the owner doesn't want to pull the engine to fix the magneto. By the way, you won't need to change the battery and generator/alternator if you go to coils and magneto. The magneto is a separate ignition source so when you flip the switch from batt to mag you disconnect the ignition from the battery and connect to the magneto.
Anyway, If it were mine I would do the least expensive in both work and money to enjoy the car and then if some time in the future, you want to make it more original, you can always convert it back to 6 volts.
Thank you to everyone for your valuable comments and advice.
I haven't purchased the T yet, but, will make an offer because I now feel more comfortable about its 12 volt conversion.
If my offer is accepted and because the T has a 12 volt system, I'll go to Costco to buy an air conditioner and Sams Club for a refrigerator as noted by other forum members. It is a Runabout so the fridge can be fitted into the turtle deck and the air conditioner can be hung from the top bows. Maybe a stereo and TV also. lol lol
I think with that attitude, you're going to enjoy the hobby a lot. I am of the "original" camp, but also know that Model T's are fun, no matter what flavor they come in.
Good luck with your search and keep us informed.
Tony B depends on what part of the world
12v or 6v battery price i get 12v myself
Why cheaper and can be had fare more choices since i dont run a starter thats same as a waterpump coils for starting and lights .
One more plus is you can wire in a USB plug charge your cell
Jay- Tractor Supply Company, 1400+ stores throughout the US, been in business since 1938.
528 NORTH MAIN ST SR9
COLUMBIA CITY, IN 46725
Exide 6 volt battery in stock- $79.99
It's a myth that 6 volt batteries are hard to source- and at $79.99 they're cheap.
I'm running an Interstate 6 volt. It's been in the car 10 years, and it spins the engine over like a 12 volt. Any one who thinks they need a 12 volt battery is nuts!
Sounds like we are reinventing the wheel. A properly maintained six volt system worked for Ford.
I wonder why ALL the auto manufacturers switch to twelve volts?
brighter lights, less copper, lower current.
There were a couple of reasons why all the manufacturers switched to 12V. One was the increase in current drain of car electrical systems by the 1950's. Practical limitations, like generator brushes handling the higher charge current required were one thing. Also, higher current requires thicker copper conductors for any given voltage drop.
Changing to 12V halved the current flow for any given power, and allowed smaller gauge (cheaper) wiring. And manufacturers love anything that reduces production costs.
Had automotive technology remained in the Model T era, there would be no technical reason to change. The 6V system works perfectly well for the low current draw.
Interestingly, there was a push for 42V car electrical systems a few years back, but nothing ever seemed to have happened with that. Maybe the development of LED lighting dropped the current drain sufficiently not to worry about it.
Your comment about the 42 volts made me smile!!
I have a 1920 Detroit Electric and it has 42 volts in the front and 42 volts in the back. The speed control switch connects things in various combinations of series and parralel for a total of 5 speeds forward. Mine has the Edison patent iron nickel alkaline batteries
I have been running my '23 runabout for several months now using the original six volt system and a new battery. This was my first T with a starter / generator; my previous T was the old system ... with hand crank only.
I recharged the magnets when I was rebuilding the running gear and only cleaned up the starter and straightened the shaft. Put new bearings and a new brush plate insulation piece in the generator .. and undercut the turned down armature. Also got some rebuilt coils and a fun projects voltage regulator.
Anyway ... I was so surprised how nicely everything works even in the cold weather. Always starts on about the third revolution on magneto after pushing the original starter button. The regulator by the way is wonderful. Before owning this T I had read many posts about switching over to 12 volts ... and now I do wonder why people think it's necessary. My only complaint is the newer system switch assembly which is more finicky than the type on the coil box. But that's on the list to rebuild some cold snowy weekend.
sounds like you're another true believer! I agree with you that the original system works very well. The only requirement (and one that seems to be a big hurdle for some) is that you either repair or maintain your car as it was originally intended. Oy Vey! Such an obstacle like I've never seen before!
Congratulations on a successful revamp!
Mark- there are many reasons why people switch to twelve volts, I think the two main reasons are:
1. The misconception that a 6 volt system is flawed
2. Acquisition of a vehicle that doesn't work property due to an ancient wiring harness and other faulty parts.
Les Schubert, how old are your Edison batteries, and how is their capacity at this point? I have some, probably from the 50's, they are weak, but I didn't try to change the electrolyte, that's supposed to bring them back. Dave in Bellingham,WA
O'Reilly's sells 6 volt batteries and they are fairly reliable. In the 11 years that I've owned the car I think I've had to put two in. I would agree with all of the other commenters that if it is currently using 12 volt, stick to it and see how it works. After period of time and interaction with other Model T owners that have the original 6 volt system you may want to convert it back just to have the experience. My car runs better on Magneto than it does on battery, and to chime in on the coils, I have had the points become unsoldered on two separate occasions in the last 11 years and was able to limp on home on 3 cylinders until I could change the coils out. I have no qualms with a 6 volt system, although others that run on 12 volts have tried to convince me otherwise.
I drive my T nearly every day to work. Have over 650 miles on the car since I first started it in August. So it's constantly being run and maintained and that probably helps ...
If 12 volt Batteries and lamps had been readily available in 1909 Henry Ford would probably have used a 12 volt electrical system instead of 6 Volt, to save money on the smaller gage wiring.
Ditto what Tim said, but I would add:
3. The misconception that "more volts" is better.
No, "more volts" is different. Ohm's Law remains the same.
I'm in the process of restoring (and repairing) a hack-job 12v conversion on a '55 T-Bird I bought a few years back. That sort of thing does a lot of damage to a "modern" car - not only to the starter, but both power window motors, the heater fan, and handful of other electrical items. I can only hope they disconnected the original radio, which of course, doesn't work now.
Bruce I don't think we will ever stem the tide of misinformation in regards to OE 6 volt systems. For too long 6 volts had gotten a bad rap based on erroneous testimony from folks who don't know any better but heard it from some one else.
I have never understood the mentality of the people that use 'Why do modern manufacturers do........' as an excuse to modernize their antique car. Why do modern car manufacturers incorporate the headlights into the grill? You gonna do that to your T? Hey, it's yours. Do with it what you will.
When did Ford switch to 12 volts, I am thinking 56 or 57 ? Chevy went to 12 volts in 1955 best of my recollection, seems like when one Auto maker went to 12 volt they all jumped on the band wagon, What car was the first to have a 12 volt electrical system and when ?
I think it had something to do with the "Muscle Car" engine. It had higher displacement and compression. It also was the beginning of many electrically operated accessories such as Air Conditioning, power windows and, of course, the others of the "big three" were using it.
Most of the big auto parts stores have 6 volt batteries along with Tractor supply here in this area. A 6 volt system works fine in a T as long as all the electrical components are in good shape. If your starter is worn out 12 volts won't make it any better.
I went with 12 more for convenience than anything else.A 12 volt charger can be had about anywhere.A 12 battery can be jumped off safely.I am sure you can start a 6 volt T with 12 volts but I don't want to be hanging around either battery when you do it.
I can go to the local tractor supply and get a 6 volt battery. And run into to the situation I did with my 47 Pontiac.I converted it to 12 volts,generator rewired,12 v regulator and so forth. It uses a LONG 5 inch wide battery like alot of John deere tractors use.Well I gave nearly a 100 bucks for the battery and brought it home. Got 2 years of very light duty service and it was giving me trouble. Turns out it was about 3 years old.Had been on the shelf a year before I bought it uncharged.
If you buy a 6 volt or 12 for that matter, check the date sticker-code and make sure you get a fresh battery.
Dodge and some other makes had 12 volts in the teens and 20's out of the factory so it's not so much of a new thing. I have an early Bosch 4cyl magneto with a small 12v generator on the top of it and the tag says"Bosch Ignition and Lighting System" on the tag. Layden Butler posted a picture of a near identical unit on a T engine on this site awhile back so even back then there were choices.
I found this information on 6 and 12 volt operation in a model T. kinda long but very in depth information, pro con explanation.
6 Volts or 12?
A common question from newcomers to Model T’s is, “Should I convert the car to use a 12V electrical system”? The response might be, “What’s wrong with the 6V system it came with”? The purpose of this article is to explain the situation with both systems.
What voltage for cars?
In the early days of electric starting and lighting, 6V became standard with most cars. An objection to higher voltages was that the lamp filaments had to be thinner and longer (i.e. more fragile), and thus gave shorter life with excessive vibration from dirt roads. Nevertheless, a few luxury cars did use 12, 18, or 24V for their electrical systems.
Wiring resistance, and starter motor current draw, make anything less than 6V impractical, so the three cell battery became standard for most American cars, including Ford, up until around 1954.
The 1950’s and 12V.
6V served the auto industry well, with everything from cars to trucks and tractors using it, without any inherent problems. However, in the affluent 1950’s of the U.S., cars were placing increased demand on their electrical systems. Cars now had heaters, air conditioners, power windows, electric seats, more powerful headlights, and so on. The problem here was keeping the battery charged. A typical automotive generator can only provide about 20 Amps before the brushes and commutator overheat. How to get more power? Seeing as the current is limited, the voltage then has to go up. 6 Volts at 20 Amps is 120 Watts. But, if we make the generator voltage 12, then we can have 240W without overheating the generator. And so the problem was solved effectively, until alternators with their much higher output, became available. A further advantage of using 12V was that the thickness of the wiring could be reduced, saving copper costs. This comes about because for the same power, the current is half of what it is at 6V. It is current flow that causes voltage drop in the wiring.
12V and the Model T.
The first documentation regarding 12V in a Model T appears to be an old Vintage Ford article, where a decrepit T was found, and having difficulty getting the starter to work, the owner decided to try a 12V battery. Effectively, it was made to work by brute force; which it apparently did quite well. He also found the coils worked off the higher voltage, and the generator charged. After replacing all the light bulbs he continued to use it this way. Word got around that this was a way to “fix’” hard to start cars and so began the trend.
Let’s look at some of the reasons owners give to use 12V in a Model T today:
• Poor starter motor performance at 6V
• Poor light output from headlamps
• Dead magneto and a desire to retain the Ford coils
• Ability to use modern accessories such as GPS or CB radios
• Easier to obtain bulbs and batteries.
Poor starter performance.
Starter motors barely able to turn, and dim orange headlights, are not in fact, a characteristic of 6V electrical systems. Instead, they are indicative of an electrical system in poor condition, or one that has been poorly rebuilt.
Often, a starter motor is pressed into service with nothing more than painting it black. That the commutator or brushes may need attention, the windings may have shorted turns, or the bushings may be worn, are conveniently overlooked. And, if the car has been rewired, it may well have an incorrect gauge of starter motor cable fitted. The starter switch too, may have merely had the black paint treatment, ignoring the high resistance burnt contacts within.
And so, with the car ‘restored’ to a gleaming state, in goes a 6V battery and what a disappointment! The starter barely turns and car can hardly start. The owner, thinking of how fast a modern car starts with its 12V battery then thinks the same should fix the T. And sure enough, with a 12V battery fitted, the starter cranks at a rapid pace and the engine bursts into life.
But, let’s have a closer look at what’s really happening here. The higher voltage battery is merely allowing for voltage to be dropped across all the high resistance points, and still provide enough to drive the starter. Or, it could be that the bushings have worn and the armature is off centre, or maybe the old oily rotting cloth insulation on the windings has partially broken down. Here, the higher current makes it work simply by brute force. Nevertheless, the owner is now convinced of the virtues of 12V, and the original 6V system is dismissed as being a serious design fault, having no place in any car.
The next scenario is the car with dim lights. The orange filaments that throw light only a few feet in front of the car, cause the owner to again think of the modern car, and its piercing white light shining for several hundred metres.
Again, 12V is seen as the cure; in go a set of 12V bulbs and the owner is convinced even more. What’s happened is the rusty chassis connections, thin wiring, and dirty switch contacts aren’t dropping as much voltage, because the 12V bulbs draw half the current, for the same candlepower. Now, had the wiring been properly restored, with correct gauge cable, and good clean connections, it would have been noticed the 6V bulbs gave out the same amount of light. Light bulbs in the early days were rated in candlepower. That’s the amount of light it puts out, regardless of anything else. So, a 32CP bulb puts out 32 candlepower of light whether it is 6, 12, or even 240V. The optics of the Model T headlights are often overlooked as being a contributor to low light output. Unlike modern cars with their pencil beams, the T headlights provide more of a flood light. One has to realise that 32CP spread over a large area is going to appear dimmer than if it’s concentrated into a narrow beam. Tarnished reflectors only make this worse.
Coils work better at 12V if no magneto.
For those without a working magneto, 12V is seen as the next best thing. And indeed, results are good. But is it actually necessary? Coils performing poorly at 6V are usually a result of them being in poor condition to start with, or other ignition troubles. Again, by means of brute force, 12V often ensures a good spark. See here for further information.
This is one of the most common reasons for the switch to 12V, but in many situations 6-12V converters can be used. These are still available new, or at a considerably lower price, from swap meets. They were made for when car audio equipment became fashionable, about 40 years ago, with many 6V cars still extant. Most examples provide at least 2A at 12V. I designed and built my own here.
Where higher currents need to be drawn, there is some justification for a totally 12V electrical system, partly because the Model T generator output power is limited to only 100W. In other words, just one modern halogen headlight bulb would take it to the limit of charging capability.
6-12V converters like these can be picked up at swap meets for only a few dollars.
While it is true that 6V batteries aren’t on the shelves of every car parts supplier, is this really a problem? You wouldn’t expect to find band linings or fan belts in your local Supercheap either.
It’s not as if batteries fail all the time. It only takes a day to have one ordered in, or delivered by the NRMA; a good deal faster than obtaining most other T parts! Luckily, the T is provided with a starting handle, so in actual fact, a dead battery won’t put an end to the trip. And it’s extremely rare that a battery will be unable to provide the small current, for the ignition system in cars with no magneto. It is actually quite possible, and practical, to run Ford coils from a 6V lantern battery which is available at any corner store. This can be used as an emergency measure to complete the trip. Cars with a good magneto do not require any battery to start and run.
A point to consider is that the lead plates in a 6V battery are thicker than those of a 12V one, and there’s less of them. This in theory should give longer life. So far, I’ve had over eight year’s service with my battery.
Furthermore, is that where a 12V battery is used to drive an unmodified 6V starter motor, much more current is being drawn, than by a proper 12V starter, which can only reduce its life.
Headlamp and ancillary light bulbs are often said to be available ‘everywhere’ if you use 12V. One has to question just how often bulbs burn out, given the infrequent use most T’s get. There seems to be a fear of being stranded in the dark with no headlights, should a bulb blow, despite most T’s never being driven at night. One has to remember that with the two headlights, there are actually four filaments that have to burn out before being plunged into darkness.
The double contact bayonet headlight bulbs, even in 12V, are in fact, not used in any modern car, and are certainly not on the shelves of every service station. Seeing as they’re going to have to be ordered in anyway, this makes them no more convenient to obtain than 6V bulbs.
For those with non standard cars, even parts like fuel pumps and distributor type ignition coils are readily available in 6V. An eBay search of “6 volt” turns up some very interesting items.
This is the enemy of any low voltage electrical system, particularly where there are high current loads, such as a starter motor. Voltage drop comes about from several things:
• Wiring resistance.
• Resistance of terminals and contacts.
• Chassis connections.
• Battery internal resistance.
Wiring resistance is the result of an insufficient gauge (or thickness) of the copper conductor. The original Model T wiring harness is quite sufficient for the job, but many cars have been rewired using something of lesser gauge. While such wire might be satisfactory for 12V, remember the current draw for any given power at 6V is double. All wire has resistance, and the more current flowing, the more voltage is lost. For example, if a length of wire has a resistance of 0.1 ohms, and it’s feeding lamps drawing 120W, then 1V will be lost with a 12V system, or 2V with a 6V system. So, before rewiring your car, be sure the wire has adequate thickness. A common trap is the starter motor cable. This, as sold for 12V cars, is much thinner that what is required for 6V. The result is a very sluggish starter motor on 6V, when this has been used.
85 years of tarnishing and corrosion, of all the switch contacts, bulb socket contacts, and various terminals, also contribute to a poor electrical system. Again, 12V will mask this, but the correct procedure is to ensure all connections are clean and tight. All that’s usually needed is a clean with a scouring pad until the connections are bright and shiny. And, of course, terminals must be tight. The screws on the Fordite terminal block need to be checked from time to time as they do loosen. A reproduction terminal block can be used to eliminate this problem if desired.
The starter motor.
The most serious problem is the starter switch. Here, we are switching around 150 Amps. The slightest voltage drop will cause overheating, and eventual loss of temper of the switch contacts. This can be clearly felt by holding the terminals of the starter switch after cranking the engine. That heat is power which the starter motor has been deprived of, so it’s no surprise it runs poorly.
While starter switches can sometimes be rebuilt, it is a futile exercise once the phosphor bronze leaves have lost their temper and continue to burn up. Fortunately, there is a good reproduction switch available.
The brass leaves of this switch have lost their springiness after being overheated. It is impossible to achieve reliable contact, thus causing voltage drop.
Further power can be wasted in the earth return. Does the battery earth strap get hot after cranking? If so, chances are it’s too thin and/or the connections are dirty. Are the chassis rails clean where the engine mounts sit? All the starter motor current flows through here, so is a potential point of power loss. And finally, how well is the starter connected to the hogshead? Are all four screws clean and tight? Remember, the gasket here is an insulator, and through those four screws is the only way the current can flow back to the battery. A highly recommended reliability enhancement is to run a thick gauge wire from one of these screws direct to the negative battery terminal.
Now, what of the starter motor itself? Few are so bad they won’t rotate at all, but if the windings have shorted turns, the brushes or commutator are poor, or if the bushings are badly worn, then it won’t work properly under load, and may well draw excessive current, causing further damage.
There should be at least 4.5V at the starter motor terminal and it should crank the engine quite rapidly; if not, it indicates a problem with the wiring or starter motor, not a reason to install a 12V battery.
The final thing not to overlook is clutch drag. If the car is hard to crank by hand, then the starter will be loaded down too. Again, rather than ‘force’ the starter to overcome this drag with a 12V battery, the bands and high speed clutch need to be examined. If a T can’t be hand cranked all year round to start it (back wheel jacked up or not), there are problems that need to be looked into before blaming the electric start being poor on 6V.
Usually the contacts of the ignition and lighting switch are in good condition and only need a clean. Some care needs to be taken in bending the tabs holding the fibre contact plate to the back of the switch.
Using the chassis of the car as an earth saves on wire which is why manufactures do this. And, it works well – while the metal is all bright and shiny. Once the rust has set in, and mud gets between the body panels and chassis rails, the dim light and intermittent ignition problems start to appear. Examining the headlights reveals about half a dozen chassis and body panel joins, before we get back to the negative battery terminal. One either has to keep all these clean, or more reliably, run an earth wire direct to the negative battery terminal from each electrical accessory.
The headlights themselves contain several connections before the outer bulb contact reaches the headlight body itself. The focussing mechanism is one place precious volts can be lost. Here it’s a good idea to solder a wire direct from the lamp socket to the headlight body.
To make a T run well with 6V is really nothing more than following the stock standard design, while ensuring all electrical components are in good condition. The points to observe are as follows:
• Appropriate wiring gauge for the wiring harness, starter motor cable, and battery earth strap. The reproductions are satisfactory.
• Starter motor switch with clean and springy contacts.
• Starter motor with good windings, brushes, commutator, and bushings. (A shiny coat of black paint is not a sign of these things!)
• Reliable earth returns, whether body connections are kept clean, or separate earth wires are used.
• Lighting switch contacts clean and tight.
• Headlamp sockets clean, particularly with regards to earthing.
Rate of charge.
Now we’ve got our car running successfully with 6V, what to set the third brush to? Given that the battery on charge will be around 7V, and the generator is limited to 100W, this gives about 14A maximum charge. However, this amount of current will soon overcharge the battery (unless the headlights are used continuously). It also puts needless stress on the generator. In practice, I’ve found 5A to be quite sufficient. Not only is the generator lightly loaded, but the battery won’t be damaged from over charge.
For those who wish to have a higher charge rate, the Fun Projects http://www.funprojects.com voltage regulator is highly recommended. This works by cutting off the generator output when the battery reaches full charge at 7V. It is a direct replacement for the standard cutout, looks identical, and requires no modifications.
If you’ve made your mind up that 12V is for you, then there’s a few important things that need to be considered in order to do the conversion correctly.
The only modification here is to simply change the bulbs for their 12V equivalents, and to use a 12V flasher if indicators are fitted. All these are available from the usual repro parts sources, while flashers and some bulbs can be obtained from modern car parts suppliers. For those contemplating LED indicators, beware of problems with some flashers not being compatible, and also magneto interference causing erratic operation. As the LED’s draw such a low current, it is necessary to load them down with 15 ohm 10W resistors, if these problems are evident.
Ford coils are happy with 12V as they are, but should not be left buzzing continuously. Points life will be shorter than with 6V or magneto, but still many thousands of km. Distributor ignition obviously requires a 12V coil, but check whether or not a ballast resistor is required with the coil you’re using. For example, the Bosch GT40 connects directly to 12V, whereas the GT40R requires a ballast resistor to drop the voltage to around 9V. Use of such a coil with no ballast resistor will cause it to overheat and burn the points.
The standard battery horn could be rewound with twice as many turns of wire having half the thickness. Most will find it easier to just install a dropping resistance, which is satisfactory. Here, ceramic bodied ignition ballast resistors (typically these are 1 to1.5 ohms) can be used, but it may be necessary to use two in series. The horn voltage should be checked with an analogue volt meter and resistance adjusted accordingly, to get around 6-8V at the horn terminal.
Digital meters are likely to give erroneous readings given the sharp pulses of current drawn by the horn. Motor driven “ahooga” type horns are used in some cars. If the motor windings are such that the field coils are in parallel with the armature, then the motor can be rewired so that they are in series.
Again, a dropping resistor can be used to avoid any modification, and as with the standard horn, the value has to be found experimentally.
Generator and Cutout.
The stock standard generator will in fact charge a 12V battery. This is because it has a constant current output. If, for example the third brush has been set to 5A at 6V, it will put around the same current into a 12V battery.
The third brush adjustment is much more critical and tricky to set to the exact current at 12V, and the generator is still limited to 100W. This gives a maximum 8A charge rate. However, the battery is liable to be overcharged and damaged, if constantly charged at this current, so either install the Fun Projects regulator, which is also available for 12V, or keep the charge current down to 3A. Unless the generator has been rebuilt, it is likely that the windings will be in poor condition with failing insulation, so it is worth having the generator rewound for 12V.
While the standard cutout will function, the voltage coil will be exposed to twice its working voltage. Either replace it with a diode type cut out, or again, use the Fun Projects regulator.
Some owners install alternators to obtain higher power. Something to bear in mind here is that the alternator fan has to be removed, when the alternator is mounted in the normal generator position.
This removes the forced cooling, and therefore the output available is not as high as first thought.
The Starter Motor.
This is the most awkward part of the conversion, and thus usually incorrectly done. Many owners simply put 12V into the stock 6V starter. Several undesirable things happen (which are unfortunately out of sight, and therefore out of mind). Firstly, the current flow through the windings, brushes, and commutator is higher than at 6V. Eventually, and it may take many years, depending on how much the car is used, these abused parts will fail.
Secondly, the torque of the starter motor is much increased. This puts much more stress on the Bendix, which in turns chews out the ring gear teeth faster, once it has slammed into the flywheel with greater force.
It is no surprise that Bendix failures occur more often in cars with a 12V battery and 6V starter.
Bendix Spring Resistor.
The much used “Bendix spring resistor” method of using a 6V starter on 12V is unfortunately a fallacy, although it’s better than nothing. Firstly, if 6V really was dropped across the Bendix spring, it would glow red hot. Assuming a 160A starter current, the power dissipated would be something approaching 960W! This it doesn’t, because there’s actually nothing like 6V dropped.
There are two problems using a resistor here. One is that the voltage dropped across a resistor depends on the current flow. The greater the current, the greater the voltage drop. And, the current required by the starter is not constant! The unloaded current for the Model T starter motor is much less than when it cranks an engine full of cold oil. What this means is that pretty much the full 12V appears across the starter motor as soon as the switch is activated, driving the Bendix into the ring gear at a greater force than intended. With the starter under load cranking, the current increases and the voltage now drops. But the Bendix and ring gear damage has already begun.
Secondly, it is an extremely inefficient method. As pointed out above, a lot of energy has to be wasted in heat during starting. It could be argued that this is for a very short and intermittent period of time, but the fact remains that more current is drawn from the car battery, than if a 12V starter had been used.
The same comments apply, as to when a long cable used as a voltage dropper to the starter motor.
The proper way to start a T on 12V is to have the starter rewound for 12V. Alternatively, it is possible to rewire the motor so that the four field coils are all in series with the armature. This chart comes from Ron Patterson on the mtfca forum.
As can be seen from this graph, modifying the motor for 12V will give performance much closer to 6V operation with similar torque at cranking speed. Further information on the 6 to 12V conversion can be found here.
email me: cablehack at yahoo dot com
All I can say is WOW! somebody REALLY knows what they are talking about. Thanks for spending the time with this thread and "enlightening" us.... Thanks Cablehack- really.
It truly amazes me that no one mentions an 8 volt battery....
Ha Steve......Nothing like muddying the waters!!!
I gotta say that sums it up pretty well. I especially like the part about using a bendix spring as a resistor. It does nothing to reduce the impact of the bendix slamming into the ring gear, but then it does reduce the power going to the starter to turn the engine over, right when you need it most, and the very reason people go to 12v to start with.
Here are my head lights on the OE 6 volt system:
Charlie, I just had to wade in on that...
Replace every harness with a new one. Make sure your starter switch is good and clean. You have to rebuild them, use a Regan regulator, and you should have no problem. I had my wiring looms duplicated by YandZ's in Redlands, California, because the show quality looms from a major vendor were not up to Ford standards. They even wove in the Ford tags for me.
Tim ... what 6v bulbs are you using in your headlights?
We've discussed the bendix resistor before. I'm not saying it is a perfect solution, but it does significantly reduce the starter speed at time of engagement.
Here is the previous thread thread with colorful graphs to illustrate the point:
Mark- part number 6572BX Langs.
Ahh ... ok, I’m running the same bulbs with the “better” new reflectors from Langs. I suspect they look brighter on a country road with no one in the opposite lane and no street lights. Driving in the city at night it’s hard to tell if I even have lights from the drivers seat ... though I know oncoming traffic can see mine.
Looks like about a 37% reduction, Tom. More than I would have thought.
Steve, I agree with you I am surprised no one mentioned 8 volt, Tractor Supply still sells new 8 volt batteries, and with a 33% voltage increase, and more available power all with out going off the deep end, use a 8 volt cut out on the generator and Your in business, light bulb life will be reduced some what but should be Bright till they blow then you replace them with 8 volt bulbs, does raise a problem using 12 volt converters I have never seen a 8 to 12 volt converter, Farmers have been using 8 volt batteries on their tractors and farm machinery for ever and probably create most of the demand for a 8 volt Battery that keeps them in manufacture. Almost all of the 8 volt systems seem to be electrical system enhancements since I have never heard of a factory 8 volt system,but I am sure there were some ?
I don't understand why an 8 volt battery would be recommended. If your car is wired properly and have a good functional starter why would you need a 33% voltage increase and more available power? These are some of the many things that confuse me on this forum...
I've seen this bloody thread come up every so often and to much the same result...those for the 6 volt firmly entrenched in their preference and those for 12 volt the same in their preference and that's all it really is...a "preference".
Like Steve said, you can get 12 volt goodies to work with a 6 volt set up or you can just bight bloody bullet and install a small 12 volt motorcycle battery to run your 12 goodies also. But that isn't Jay question...he's asking if he should BUY a car with this particular set up, not that he wants to make one.
Jay, it depends upon how this guy set up his car. If he did the "Full Monty" or took the "El Cheapo" route.
With the "Full Monty"
The generator has been rebuilt to accommodate the extra voltage and also sports a 12 voltage regulator or has a 12 volt alternator and then you don't need the voltage regulator.
The starter would've had to be rebuilt as already said for 12 volts.
The wiring loom is probably the same.
All the light bulb would also be 12 volt.
The horn too I suppose would have to be for 12 volts. (or you could do what I did, use a hand klaxon and not worry about it ).
And that's just about it really.
Or the "El Cheapo"
Run the 6 volt starter with some sort of voltage reducer (usually a long starter cable running the length of the car and back to the starter) or it'll have a electrical light switch box (like you get at any home improvement store) with a Bendix spring inside with insulators (pieces of plastic) between the coils of the spring.
The generator's third brush set all the way forward as far as it can go, also with a 12 volt voltage regulator.
As for that distributor...fact is all distributors work on 6 volts, the 12 volt systems have to install a resistor to knock down the voltage going to the distributor otherwise you'd burn the points (it's usually a small rectangular ceramic block located somewhere on the firewall).
As said before it would be nice if this distributor is a Bosch because those distributors usually have an automatic centrifugal advance for starting (makes it easier to start).
So far you've gotten a ton of advice, most of it good some of it off point and some of it...well you'll have to decide for yourself if it applies to your situation or not.
But if want mine...if the car is something you like and or truly want...but it! You can always switch it back to it's original 6 volt condition if and when you like.
I'm running a 6 volt system and am really happy with it always have been. I've never seen any reason to change it...as the for myth that your brighter head lights, yes and no...currently I'm running Model A bulbs 32-50's they're plenty bright enough for a slow moving car like a Model T Ford.
Now if you decide you don't want to use that distributor contraption, you can always switch back to coils and timer...just make sure your coils are rebuilt with the new capacitors you get from Lang's...they can handle 6 or 12 volts, whereas the old original Ford capacitor probably cant (it's a sandwich of foil and wax paper...it barely handles 6, don't think it would fair to well with 12...if at all...they are at least 80 years old after all).
Good point Martin. Should also add that if you want to convert back to 6 volts be sure the Magneto has not been removed and replaced with oil slingers. If it has you would probably want to factor that cost into your equation before buying the car.
I am not for one or the other however Martin, your statement that “All 12 volt distributors” have a dropping resistor is incorrect. The Bosch system used on a12 volt system in a 1967 VW did NOT use a resistor.
Maybe not an external one but I'll bet the coil had one built in. As a matter of fact I don't recall any Beetle I owned or worked on having an external resistor.
Well why hasn't someone gutted a T generator and put in a newer 2 brush design and then a standard regulator can be used like with any other 12 volt car?
There was a member of the local club had a alternator for sale 12 volt at a meeting recently. I had just bought a working generator for 100 bucks a week before and I kept thinking back to folks talking about them overheating.I think it was the Delco based 1's. And it would not look right on there either.I have a Fun projects 12 volt regulator coming in the mail in the next few days.So I will be able to give my battery back a little juice after starting.
It seems the alternator I looked at was Mitsubishi based. And I think that 12 volt starter someone posted the other day,a new replacement type was also Mitsubishi based. I know it looked alot like my Kubota tractor starter. Which has a solenoid built in. I had to replace the copper contacts recently.
Tony...There are 2 types of ignition coils, one with internal ballast resistors and one with external. Here is why a ballast resistor is used in all ignition systems in the first place.
These resistors are used to supplement the ignition coil's primary resistance. Also known as "points savers," ballast resistors have been used for decades to reduce current to the ignition coil and points, extending their lives. Otherwise you'd be going through points every other month or so.
But never fear your car has a ballast resistor somewhere, if it is not the small white ceramic block on your fire wall it's inside your coil, but it's there.
Unless it's 6v.
Many thanks once again for your valuable information regarding my questions on 12 volt conversions.
I am grateful for guiding me to be more knowledgeable about the Model T.
I will be going to see the 12 volt T within a few weeks (if the weather allows).
Am taking a printed copy of your comments with me so I can apply your advice upon inspection.
Will post findings and results accordingly.
I didn't see it mentioned here, but I have been told if you use a 12v battery you should also use 12 volt cables not the originals? Is that a fact or myth.
Not myth. Smaller cables would slightly mitigate the harsh Bendix engagement. Long, smaller cables would help even more. Please see my post with the link to the previous thread where we talked about this.
By the way, my post above assumes a 6V starter. If you are using a 12V starter, 12V cables would be of no benefit with a 12V battery. So in this case, myth.
It is my opinion that with a 12 volt battery and a 6 volt starter the minute resistance offered by smaller cables or bendix spring would not prevent the bendix striking the ring gear to hard. The starter would not see a significantly reduced voltage until it comes under the load of cranking the engine.
A somewhat different perspective on starter performance:
I was 19 when my Dad bought his '12 (hand crank) T. The 19 starter spun that engine effortlessly. Now, 56 years later, I own the same car and find that the 75 starter doesn't crank quite so fast or so tirelessly. In time, one of my kids will inherit the car and the new, younger, starter will once again spin with vigor.
Oh, yes, I should mention that my Model A still has 6V. And for me the biggest benefit of the 6 volt system is seeing the sympathetic look in the eye of every first-time passenger. The unspoken message is always the same: "Ain't gonna start. Ain't gonna start. Battery's about dead. I'm so embarrassed for you. Wow, it actually started. Bet that was the last start on this old jalopy".
I love telling those latter day experts that the Model A has sounded like that for more than 80 years and will be starting and running reliably when their MazToyNisHonda has been recycled into beer cans.