Alternator: Testing and Inspection
INSPECTION1. DIODE
CAUTION: There is the possibility of damaging the diodes if a mega-tester (used to measure high voltages) or a similar measuring instrument is used. Never use a mega tester or equivalent for this test.
1. Check the positive diode
Check for continuity between the diode lead and positive side heat sink. If resistance is 1 ohm or less only in the direction from the diode lead to the heat sink, the positive diode is OK.
2. Check negative diode
Check for continuity between the negative side heat sink and diode lead. If resistance is 1 ohm or less only in the direction from the heat sink to the diode lead, the negative diode is OK.
2. ROTOR
1. Slip ring surface
Inspect the slip rings for contamination or any roughness on the sliding surface. Repair the slip ring surface using a lathe or sand paper.
2. Slip ring outer diameter
Measure the slip ring outer diameter. Replace the rotor assembly if the slip ring is worn.
Slip ring outer diameter:
Standard 22.7 mm (0.894 in)
Limit 22.1 mm (0.870 in)
3. Continuity test
Using a circuit tester, check the resistance between slip rings.
If the resistance is not within the standard, replace the rotor assembly.
Specified resistance:
Approximately 1.8 - 2.2 ohms
4. Insulation test
Check the continuity between slip ring and rotor core or shaft. If the resistance is 1 ohm or less, replace the rotor assembly because the rotor coil is grounded.
5. Ball bearings (rear side)
Check the rear ball bearing. If there is any noise, or the rotor does not rotate smoothly, replace the bearings.
3. STATOR
1. Continuity test
Inspect continuity between the stator coil lead wire terminals. If the resistance is 1 Mohm or more, the lead wire is damaged. Replace the stator assembly.
2. Insulation test
Inspect the continuity between the stator coil stator core and lead wire terminals. If the resistance is 1 ohm or less, the stator coil is grounded. Replace the stator assembly.
4. BRUSH
1. Measure the length of each brush. Replace the brush if wear exceeds service limits. There is a service limit mark (A) on each brush.
Brush length:
Standard 18.5 mm (0.728 in)
Service limit 5.0 mm (0.197 in)
2. Check that there is appropriate pressure on the brush spring.
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 brush spring. If the pressure is 2.648 N (270 g, 9.52 oz) or less, replace the brush spring with a new part. 4.609 - 5.786 N (470 - 590 g, 16.58 - 20.810 oz) pressure is required on the new spring.
5. BEARING (FRONT SIDE)
Check the front ball bearing. Replace the ball bearings if there is resistance in the rotation, or if there is any abnormal noise.