1923 Model T generator stopped working

I have a 1923 model t. The generator gauge/am meter has been working up to this point. Today it stopped working. Can anyone suggest ideas to me to check for whether it’s generator or the gauge.

The gauge is easy to test. Switch on the headligths - if the needle goes towards 10 - 15 amps discharge the gauge is working.
The generator is more tricky. And there is a cut-out relais that may be the culprit. Start the engine and let it run at slightly high idle (so that you’ll expect some charge from the generator). Then take a little piece of 8 - 10 gauge wire and shortcut the cut-out on top of the generator. If it now shows some charging, the cut-out is the culprit. If it’s a traditional reais type, consider swap it with a proper diode based one.
If that didn’t make it - well - it’s time to take of the generator and start setting 6 or 12 volts to it and see if it runs as a motor. It should and it should be fairly strong if you try to hold it on the drive. It may not have “white spots” where the engine can be set and not running (armature have bad connections). Apart from the armature, which really should be tested on a growler, I can think of worn brushes or broken insulator at the brushholder.

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The advice from dykker5502 is on the money.

I’d like to add to the thread from my own personal experience. We have a similar experience once or twice a year with one of our T Models. A thin film of motor oil makes its way to where the brushes ride. When this happens I remove the band exposing the brushes. With the engine running slightly above an idle I LIGHTLY spritz the brushes with some aerosol brake cleaner. If one application doesn’t do the trick, after waiting a few minutes, I’ve found one or two more LIGHT spritzes do the job. Hope it’s that simple.

Regards, Tom in Taylor Mill KY 41015