1915 Model T Magneto

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Doug 845

Senior Member
I am considering buying a 1915 T. The problem is it doesn't run on Mag alone but needs a battery. How big a deal is this? How much work & cost would it take to fix this correctly?
 
There are several key components to have a proper functioning original magneto - magnet strength, a field coil with no shorts or opens, serviceable limit of air gap (.025 - .040) between magnets & field coil and serviceable limit (very important) of end play (.004 - .006) on rear main bearing to maintain air gap - all internal components that would require engine removal & tear-down. External components are the magneto contact on transmission cover, commutator, coilbox, coilbox switch and coils. A considerable amount of money could be spent in an attempt at correcting a non-functioning magneto. There are several "to do" procedures to assist in trouble shooting the cause prior to engine removal.
 
Steve just about covered it all.
Diagnosing and fixing a mag can be simple or complicated.
Some people just give up and run on the battery
In some cases people remove the mag completely during a rebuild.
But the Model T runs best on a Mag unless it has a distributor.
 
As stated could be as simple as cleaning the contacts in the coil box switch, cleaning the contact on the hogs head, making sure the wires are in the correct place and are hooked up correctly or an in car recharge of the magnets. Or a complete tear down and rebuild. Try doing a google search; "mtfca; magneto" you should get a bazillion hits. Ok maybe not that many but more then enough info on testing etc of the magneto.
Adding to that, there is more to the job then just replacing the parts. Read some of the post and get a feel for what it will involve in the job, don't just jump in and find you are over your head time, money, tools and skill. You never know what you will find hiding inside that will need attention. There are some special tools needed for the job.
Remember many people have and can work on a T but even in the day some took it to a shop to get fixed.
 
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The other guys have covered it very well. If you were only starting on BAT and running on MAG, you could go for months without a recharge. But running only on BAT is another story. The ideal is to have such a good magneto that you don't need a battery, even for starting. But if it's not working at all, fixing it can range from simple and cheap to complex and costly, depending on why it isn't working.
 
I have one Model T with a bad Mag and I have been running it on Battery for 5 years.
They run great on a 12 volt battery and I just use a lawn mower battery and I will do
a whole weekend long tour with plenty to spare even using the same battery for a brake
light. The only real down side is that it causes the points on the Ignition coils to build up
a little bump on them that doesn't happen when you use the mag. You can lessen this
problem by reversing the polarity of the battery every once in a while.

My 2 cents....
 
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