Alternator Components Tests and Inspections

ALTERNATOR COMPONENTS / TESTS AND INSPECTIONS


Rectifier Test

NOTE: The diodes are designed to allow current to pass in one direction while blocking it in the opposite direction. Each diode must be tested for continuity in both directions with an ohmmeter that has diode checking capability. Since the alternator rectifier is made up of eight diodes (four pairs), there are a total of 16 checks.







1. Check for continuity in each direction between the B and P terminals, and between the E (ground) and P terminals of each diode pair. All diodes should have continuity in only one direction.
2. If any of the eight diodes fails, replace the rectifier assembly. (Diodes are not available separately.)


Alternator Brush Inspection
1. Remove the end cover, then take out the brush holder by removing its two screws.







2. Measure the length of the brushes with a vernier caliper.

Alternator Brush Length:
Standard: 10.5 mm (0.41 in)
Service Limit: 1.5 mm (0.06 in)

If the brushes are less than the service limit, replace the brush holder assembly.


Rotor Slip Ring Test







1. Check that there is continuity between the slip rings.
2. Check that there is no continuity between the slip rings and the rotor or rotor shaft.
3. If the rotor fails either continuity check, replace the alternator.


Stator Test







1. Check that there is continuity between each pair of leads.
2. Check that there is no continuity between each lead and the coil core.
3. If the coil fails either continuity check, replace the alternator.