Hi
I have not done this yet but here goes
Unplug the Dizzy electrical connector.
Conncet 12v from the battery to the outside terminals. Check the spare dizzy to see which is +ve and which is -ve.
Connect a digital voltmeter to the middle terminal.
As u turn the rotor, you shoulg get 0 volts then 2 volts then 0 volts then 2 volts.