While using an HCCT to test a coil, hand cranking it typically produces about 4-6 volts, and if I connect an 1156 bulb only (no coil), it will light it dimly. If I remove the bulb and test a coil, again at the 4-6 volts, it will draw 1.3 amps and spark 16 times. If so, how strong must a mag be? I read it needs to burn the 1156 bulb dimly at 6 or so volts at idle, but then at speed must go to 25v and burn out the bulb. I guess my question might be if a mag can light the bulb dimly at idle will it be good enough to at least operate the coils at idle and allow the engine to run?
I use a HCCT to test all the coils I repair also the Heinze, Kingstons and other.
If the coils are set right you don't need 4-6Vac to make them spark, I saw Heinze coils start sparking under 1Vac.
While hand cranking you engine, the magneto will never give you 4Vac because of the turning speed is much lower as on the HCCT during the coil tests.
With coils set right and a normal working magneto You should be able to start your engine on magneto.
That how the Model T engine is build.
The battery was only added to easy the cold start up.
Maybe this helps
I forgot to mention the most important to make the coils spark is not the tension but the current.
So, on a friends T, at idle, the 1156 bulb lights a little more than dim. At fast speed, the bulb gets bright, but not super bright like it does on my T. So I assume the mag could be stronger. But, should one think it would be enough, at least at idle, to allow it to run on mag? The bulb, at idle, is much brighter than what the bulb is on my HCCT while hand cranking. It seems to me it should idle on mag.
If i understand your question, yes i always run on mag, only use bat to get it started then switch to mag. Runs great at idle on mag. I have even started it on mag with no problems including hand cranking on mag provided i advance the spark rod a few notches first.
Jeff, that is not my question. I know when all is good, a T will run great on mag at all speeds. I am basically asking how weak a mag can be and still operate the engine, at least at idle.
I don't know how weak a mag can be, before the ignition stop working properly.
I ones did an in car magneto recharge with a 12V and a 6V battery. After the car runs great on magneto and it still does, this was 6 years ago. Photos are taken just after the recharge and are from idle to 3/4 throttle during the test drive after the recharge.
You know that the coils are set at 1.3A current.
On the HCCT, While testing a good coil, you will see that the current the coil need to start sparking is a little higher as the 1.3A the coil was set on.
For me, a magneto that can produce the needed current to make the coils buzz what ever the tension is, is a good magneto.
To test a magneto I use a 12V 21W light bulb( substitute for the 1156 bulb here in Belgium).
The current on the bulb is 1.75A, the current needed to allow the coils starting to buzz.
I am in the same struggle but with a restoration project of my HCCT. I am using a Harbor freight Digital meter and a tester the kind with a clamp and a pointed probe end that has a lighted internal 6V/12V bulb. I recharged the magnets with a battery charger as shown on YouTube by placing the Coil ring over the magnets North to South and zapping the assembly, it seem to have worked. But I canít get a spark on the spark ring most of the time, the volts reads only 3.4 AC volts and the bulb is very dim. Is this a case where the Coil ring is bad, I did check the resistance and was very low about 1.2 ohms. I donít want to tread on a post but hope to share my experience to help you and me. Thank you. Erick
1.2ohm is ok for the coil ring. 3.4Vac should be ok too.
Don't try the coils with the test light connected.
The light will light up but the coil will NOT buzz.
I know just one way to test a magneto coil ring.
Out of the engine. Make a loop with a 12V battery, a 21W 12V test light and the magneto coil ring.
As the light lights up go with a compass before each coil. You should see the needle go from N to S to N and so on.
Leaving for the model T concentration in Blois France next weekend.
Update- with an analog voltmeter and an 1156 bulb for a load, at idle I had 4-5 VAC, 10 VAC at a speed. The engine would not run on mag. Did an in car magnet recharge, now have 7-8 VAC at idle, about 20 VAC at speed. Car now runs on mag. I believe the magneto is still weak, but it does run.