Alternator: Testing and Inspection

Rotor Inspection (75A)



1. Check the rotor coil for continuity. Check to make sure that there is continuity between the slip rings. If resistance is extremely low, it means that there is a short. If there is no continuity or if there is a short circuit, replace the rotor assembly.
Resistance value : Approx. 3.19 Ohms




2. Check the rotor coil for ground. Check to make sure that there is no continuity between slip the ring and the core. If there is continuity, replace rotor assembly.

Stator Inspection (75A)



1. Make a continuity check on the stator coil. Check to make sure that there is continuity between the coil leads.if the is no continuity, replace stator assembly.




2. Check the coil for grounding. Check to make sure that there is no continuity between the coil and the core. If there is continuity, replace the stator assembly.

RECTIFIER TEST



Positive Rectifier Test
Check for continuity between the positive rectifier and stator coil lead connection terminal with an ohmmeter. The ohmmeter should read continuity in only one direction. If there is continuity in both directions, a diode is shorted.
Replace the rectifier assembly.




Negative Rectifier Test
Check for continuity between the negative rectifier and the stator coil lead connection terminal. The ohmmeter should read continuity in only one direction. If there is continuity in both directions, a diode is shorted, and the rectifier assembly must be replaced.




Diode Trio Test
Check the three diodes for continuity by connecting an ohmmeter to both ends of each diode. Each diode should have continuity in only one direction.
If continuity is present in both directions, a diode is defective and the heatsink assembly must be replaced.