When the tractor starts and generator begins to produce electricity, current flows from A 1 (white wire) to Indicator Light. Wiring on the 4010 and some 4020 series) provides little if any safety factor as has been local sex London evidenced by many owners of 4010's and 4020's who found their tractors suddenly catching fire. An open circuit here would cause the solenoid switch to engage and then immediately disengage and continue as long as the starting button is held. Insert feeler gauge (0.017) between armature and core.
24 volt battery hookup
The voltage is always at each terminal, however it is electrically neutral, or not flowing. Connect a volt meter to the BAT terminal and the other lead to GND. A bad battery connection will melt the battery post or connection and open the circuit. Take one 12 volt system off the tractor and what is left is a typical 12 volt system. Any ground within the 24 volt system will cause current to drain from the batteries. The return circuit is carried back to the battery by wires instead of through the frame. Run engine at high RPM and turn on lights. A 2 to positive terminal of right side battery.5 volt max. Battery A negative post to starter solenoid terminal nearest front of tractor. 12 volt system controlling the opposite side of the tractor.
Airgap: move relay armature toward core until points just close. Connect voltmeter and ammeter in series with carbon pile resistor to terminals A 1 to. Stop and restart engine. Generator produces it's own current to increase magnetism in field coils, controlled by Black wire from Gen F to Regulator.