The ammeter in the video is showing battery charging.
Assuming nothing is miswired, two possibilities:
1. Battery needs charging.
2. Battery doesn't need charging but the alternator is offering power at high voltage. Result is overcharging.
Check the voltage at the battery while the engine is running and ammeter is showing charging.
It should be between 13.9 - 14.9 Volts.
If its over 15 Volts, then check the voltage in the ignition circuit connection to the voltage regulator.
That will get you started on diagnosing.
I noticed that in the video. It makes no sense as far as the gage goes. The ammeter needle movement is trom the magnetic field created by the current going around it.
Will need to think about that.
It would have been easier to test on the bench but can do some testing on the car depending on what you can scrounge up.
However I am a bit confused because in the video the gages are all pegged!