Whilst the ammeter on my 56 Dominator 99 does show a positive charge when the engine is running , I am curious in that it shows a lesser positive charge when the engine is not running. The needle does not return completely to zero when the engine is switched off.
The ammeter looks like an after market one ( no named markings on it's face ) and the two terminals each show 6v when the engine is not running . Is this correct ? I intend to disconnect the terminals to see if the needle returns to zero but I thought that I would pose the question first.
Sounds like a bent needle! One of mine fell off and had to be araldited back...Surrey roads...
so I wouldn't expect and exact zero. I would live with it but if it bothered me they're easy enough to rebuild, bending the needle appropriately.
I agree that most ammeters are pretty low-precision devices. You will see 6 (or 12) volts on both terminals (relative to earth) as the ammeter is very low resistance.
If the engine is not running and the ignition switch is switched on, will there not be a power draw (loss) through the resistance of the wiring and coils if the points are closed?
The is no ignition switch on a 56 Dominator. Ignition is via a magneto.
If the engine vibrations don't settle the needle to zero when it is ticking over, tap the glass with your knuckle after stopping the engine.