When wired correctly the ammeter will show current in/out of the battery. Yours is wired [strikethrough]correctly[/strikethrough] backward since it shows the battery is charging with the tractor NOT running. Once the tractor is running all the power for ignition and accessories is provided by the alternator, not the battery.
When you turn the switch on the ammeter will only show discharge if the points are closed. If the engine happens to stop with them open the ammeter won't read anything when you switch on. On my H the engine generally seems to stop with the points closed. The ignition system on my H is in good condition. If the point gap were incorrect or the timing off it might not tend to stop with the points closed.
My H has a 1 wire alternator. If I were to start it as in your video it won't charge at all, it needs the engine to first be revved up a bit so the alternator excites itself. If i immediately throttle down it shows very little charge as yours does. I need to run it at about half throttle for the gauge to read 5+ amps. As the battery comes up to full charge the ammeter drops close to 0 regardless of engine speed.
It's not a volt meter, it will read 0 if the electrical system is in balance. It'll read (-) if you're discharging the battery and (+) if the tractor is charging the battery. If you've got the battery hooked to some external charger or boost box the gauge might pretty much read 0 when the tractor is running since your external device is keeping the battery topped off.
As an aside: The crankshaft pulley on an H is small and the maximum engine RPM is about 1800. You cannot expect the alternator to do much unless the engine is cranked up.
When the battery on my H died I could boost the tractor and the gauge stayed low even with the engine running fast.
I'd try throttling the engine up and see if the gauge moves up. If not I'd throw a volt meter on the battery and see what it read at full throttle. If it's 13 volts or higher the charging system is working fine.
