MTFCA Forum

T runs well on mag, but not on 6 volts. Is this a coil problem?
Bob Giles

With a matched set of coils adjusted for max. performance on AC magneto current, running on 6v DC will be less than satisfactory.

My T’s have proper adjusted coils, and starting on BAT, then switching to MAG, produces noticeable rpm’s and greater power and smoother engine.

If you run 12 volts you will find the coils perform almost as well as they do on Mag. To some extent it is a matter of how the coils are adjusted. I ran one car for a year on 6 volts until I rebuilt the mag and adjusted the coils for maximum performance running it that way. Once the mag was redone I readjusted them to run best on mag. It makes a difference.

Could be the higher magneto voltage is making the coils work better by brute force from the higher voltage. There's a number of variables which would be responsible for poor 6V performance. 6 volts will work the coils very well if the capacitors in them have been replaced and the coil points adjusted correctly. Also, I have found some spark plugs perform poorly, but others such as Champion X make all the difference. Then there's the question of the timer condition. The adjustment of the initial timing is important because of the slower firing time on 6V. With everything as it should be, 6 volts on the coil will get up to about 75km/h (47mph). This is not a fluke just with my car; I have worked on two others similarly set up, with the same performance.
Generally, an ignition system in original condition with non rebuilt coils, and/or coils that have been adjusted with makeshift methods, and a dirty old worn timer, won't work well on 6V.

I ran one for about 10 years on 6 volts. With the coils properly adjusted, it should run smoothly on 6 volts however it will be slower, especially going uphill. The magneto will provide a certain amount of automatic spark advance because the voltage rises faster as your engine speeds up. Since it runs OK on magneto, I would suggest that you tune up the coils using a coil tester.
Norm

Robert

My reply inferred and means, yes, your T will run less smoothly on 6v, when you are running smooth on magneto. Obviously your coils are set for best performance on MAG.

Occasionally I will forget to switch to MAG from BAT after starting and run down the road and wonder? what's up, she ain't purring good, sluggish, oh geez....forgot to switch. Instant correction, just by going on MAG!

Years ago learned that first hand, you must have your coils tested/set on either ECCC, StroboSpark, or HCCC if you run on Ford's magneto. Nothing else!

Of course those trembler coils are very adaptable and using 6vDC or even 12vDC, if no flywheel magneto can give you decent performance. However, these coils were designed for AC current from the magneto.

Used to just 'ear' test for best buzz, look for 'bright spark' at the new points and run the T. Worked back then for what I thought was OK....an operating old Ford, with original engine and trans.

Complained at one tour where coils were being gratis set on a HCCT. Complained my T had weak magneto, as when I slowed down to idle, or low speeds, needed to switch from MAG to the 6v BAT for the motor to run right.

Well, had them there coils adjusted right on the spot, same points, put the set back in the T just as I took out, nothing changed only now the coils were adjusted the right way on the right equipment.

Wow...instant smooth best running the old '24 ever had on MAG. Could idle on MAG, could even start on MAG which I tried and could not do before, always blaming weak magnets......nope, justly properly set coils was all my Ford needed.