Alternator: Testing and Inspection
Rectifier TestNOTE: 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 eight diodes (four pairs), each diode must be tested for continuity in both directions with an ohmmeter that has diode checking capability; a total of 16 checks.
1. Check for continuity in each direction, between the B and P, 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 alternator brush assembly.
Rotor Slip Ring Test
1. Check the resistance between the slip rings.
There should be 2.9 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
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.
Alternator Belt Inspection and Adjustment
NOTE: When using a new belt, first adjust the deflection or tension to the values for the new belt, then readjust the deflection or tension to the values for the used belt after running engine for five minutes.
Deflection method:
Apply a force of 98 N (10 kg, 22 lb), and measure the deflection between the alternator and crankshaft pulley.
Deflection:
Used Belt: 9.5 - 11.5 mm (0.37 - 0.45 in)
New Belt: 7.0 - 8.0 mm (0.28 - 0.31 in)
NOTE: If the belt is worn or damaged, replace it.
Belt tension gauge method:
Attach the belt tension gauge to the belt and measure the tension. Follow the gauge manufacturer's instructions.
Tension:
Used Belt: 390 - 590 N (40 - 60 kg, 88 - 130 lb)
New Belt: 780 - 980 N (80 - 100 kg, 180 - 220 lb)
NOTE: If the belt is worn or damaged, replace it.
If adjustment is necessary:
1. Loosen the mounting bolt and the lock bolt.
2. Move the alternator by turning the adjusting rod to obtain the proper belt tension, then retighten the bolts.
3. Recheck the deflection or tension of the belt.
NOTE: For the power steering pump belt and A/C compressor belt adjustments.