MTFCA Forum

Ammeter is on the battery circuit and is separate from magneto. If generator is putting out ammeter should show a pos. If you have no generator output and car is running on bat, and, or the lights are on and or the horn is blowing, the ammeter should show a neg. If the generator is putting out and you see a pos on the ammeter, then turn on the lights, the ammeter may go to zero or into neg. How far pos ammeter goes with lights off depends on how the third brush is set. If you drive the car for long distinces, you should set the third brush to give a low charge. If you drive short dist, set for higher charge.

The meter should read up to 10 amps with the lights off and at a fairly good engine speed. If there is no charge the very first place I would troubleshoot is the generator cut-out. Simply jump around it with a jumper on each of the cutout posts. If it registers a charge then you have found the issue. After that I would use a volt meter to see if the generator is putting out any charge.
Stu

What is the procedure for testing the output of the generator?

I would firstly assure that the commutator is clean, just a slight film of oil will prevent it from charging. The generator should be sealed from the crankcase but a slight vapor leak can contaminate the commutator.

Here are a couple of relevant articles by Ron Patterson:
https://modeltfordfix.com/adjusting-the ... patterson/

https://modeltfordfix.com/the-model-t-f ... patterson/

So if the ammeter is on the battery circuit, if you run your car on mag, is the battery being charged? I start my car on battery then switch it to mag right away. Does the mag charge the battery?

One other thing I will mention. If you are using an alternator, you would show some charge at idle, but on a T generator, it will not show a charge until your engine is either on a fast idle or driving along.
Norm

"So if the ammeter is on the battery circuit, if you run your car on mag, is the battery being charged? I start my car on battery then switch it to mag right away. Does the mag charge the battery?"

The only thing that changes when you switch to mag is the feed to the coils. Everything else stays with the battery. The generator continues to charge the battery.

The magneto does not charge the battery but it can be set-up to do so. Remember the magneto puts out AC voltage. But since you have a generator it would be more complicated to do so and then whats the point.
http://www.mtfca.com/discus/messages/70 ... 1498438118
useful discussions on how to charge a battery from your magneto
http://www.mtfca.com/discus/messages/41 ... 1416288062
If you look at the wiring diagram yellow connection points show the path from the generator to the ignition switch and battery. The red connection points are fro the magneto. The ignition switch is actually two switches: the key i used to select the voltage source and the lever to select the lights