Mitsubishi
ALTERNATOR COMPONENTS / TESTS AND INSPECTIONSRectifier Test
NOTE: The diodes are designed to allow current to pass in one direction while blocking it in the opposite direction. Since the alternator rectifier is made up of nine diodes, each diode must be tested for continuity in both directions with an ohmmeter that has diode checking capability; a total of 22 checks.
(Mitsubishi):
1. Check for continuity in each direction between
- the B and P terminals.
- the B' and P terminals.
- E (ground) and the P terminals.
All diodes should have continuity in only one direction.
2. If any of the diodes fails, replace the rectifier assembly. (Diodes are not available separately.)
Rotor Slip Ring Test
1. Check the resistance between the slip rings. There should be 1.8 - 3.0 Ohms.
- If resistance meets the specification, go to step 2.
- If resistance does not meet the specification, replace the alternator.
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
(Mitsubishi):
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 core fails either continuity check, replace the alternator.
Alternator Brush Inspection
1. Separate the drive-end housing from the rear housing as described in rectifier removal.
2. Separate the rear housing from the stator/rectifier assembly by removing the four screws and the terminal nut from the rear housing.
Brush Length (Mitsubishi):
3. Measure the length of the brushes with vernier calipers.
4. If the brushes are less than the service limit, replace them.