FIELD WINDING TESTS:

 The rotor field winding may be checked electrically for open circuit, ground circuit and short circuit.

To check for open circuit, touch a 110 volt test lamp prod to reach slip ring. If the lamp fails to light, the field winding is open.

To check for ground circuit, touch one 110 volt test lamp prod to either slip ring and the other test lamp prod to the rotor shaft. If the lamp lights, the field winding is grounded.

To check for short circuit, connect a 12 volt battery and an ammeter in series with the two slip rings. The ammeter should indicate approximately 2 amperes. An ammeter reading above this value indicates shorted field coil winding. High output alternators will have a higher field current draw.

 If an ohmmeter is available, these three tests can be conducted by measuring resistance values.

FIELD WINDING TESTS