Alternator: Testing and Inspection

INSPECTION

1. DIODE

CAUTION: Never use a megatester (measuring use for high voltage) or any other similar measure for this test; otherwise, the diodes may be damaged.




1. Checking positive diode
Check for continuity between the diode lead and the positive side heat sink. The positive diode is in good condition if continuity exists only in the direction from the diode lead to the heat sink.




2. Checking negative diode
Check for continuity between the negative side heat sink and diode lead. The negative diode is in good condition if continuity exists only in the direction from the heat sink to the diode lead.

2. ROTOR
1. Slip ring surface
Inspect slip rings for contamination or any roughness of the sliding surface. Repair slip ring surface using a lathe or sand paper.
2. Slip ring outer diameter
Measure slip ring outer diameter. If slip ring is worn replace rotor assembly.

Slip ring outer diameter:
Standard 22.7 mm (0.894 in)
Limit 22.1 mm (0.870 in)




3. Continuity test
Check resistance between slip rings using circuit tester.
If the resistance is not within specification, replace rotor assembly.




4. Insulation test
Check continuity between slip ring and rotor core or shaft. If continuity exists, the rotor coil is grounded, and so replace rotor assembly.




5. Ball bearing (rear side)
1. Check rear ball bearing. Replace if it is noisy or if rotor does not turn smoothly.
2. The rear bearing can be removed by using common bearing puller.

3. STATOR




1. Continuity test
Inspect stator coil for continuity between each end of the lead wires. If there is no continuity between individual lead wires, the lead wire is broken, and so replace stator assembly.




2. Insulation test
Inspect stator coil for continuity between stator core and each end of the lead wire. If there is continuity, the stator coil is grounded, and so replace stator assembly.




4. BRUSH
1. Measure the length of each brush. If wear exceeds the service limit, replace the brush. Each brush has the service limit mark (A) on it.




2. Checking brush spring for proper pressure Using a spring pressure indicator, push the brush into the brush holder until its tip protrudes 2 mm (0.08 in). Then measure the pressure of the brush spring. If the pressure is less than 2.648 N (270 g, 9.52 oz), replace the brush spring with a new one. The new spring must have a pressure of 4.609 to 5.786 N (470 to 590 g, 16.58 to 20.81 oz).

5. BEARING (FRONT SIDE)
1. Check front ball bearing. If resistance is felt while rotating, or if abnormal noise is heard, replace the ball bearing.
2. Replacing front bearing
1. Remove front bearing retainer.




2. Closely install a fit tool on the bearing inner race. Press the bearing down out of front bracket with a hand press or vise. A socket wrench can serve as the tool.
3. Set a new bearing and closely install a fit tool on the bearing outer race. Press the bearing down into place with a hand press or vise. A socket wrench can serve as the tool.




4. Install front bearing retainer.