Alternator: Testing and Inspection

Rectifier 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 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.

Rectifier Test (Nippondenso Alternator):

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.

Alternator Brush Inspection:

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

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

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

Alternator Belt Inspection And Adjustment-Deflection Method:

Deflection Method:
Apply a force of 98 N (10 kgf, 22 lbf), and measure the deflection between the alternator and the crankshaft pulley.

Deflection: 8 - 10.5 mm (0.31 - 0.41 in)

NOTE: On a brand-new belt (one that has been run for less than five minutes), the deflection should be 4.5 - 6.5 mm (0.18 - 0.26 in) when first measured. If the belt is worn or damaged, replace it.

If adjustment is necessary:
1. Loosen the through bolt and adjustment locknut.
2. Turn the adjusting bolt to obtain the proper belt tension, then retighten the nut and through bolt.
3. Recheck the belt deflection.

Alternator Belt Inspection And Adjustment-Belt Tension Gauge Method:

Belt Tension Gauge Method:
Following the gauge manufacturer's instructions, attach the belt tension gauge to the belt, and measure the tension.

Tension: 490 - 590 N (50 - 60 kgf, 110 - 132 lbf)

NOTE: On a brand-new belt, (one that has been run for less than five minutes), the tension should be 1030 - 1130 N (105 - 115 kgf, 231 - 254 lbf) when first measured. If the belt is worn or damaged, replace it.

If adjustment is necessary:
1. Loosen the through bolt and adjustment locknut.
2. Turn the adjusting bolt to obtain the proper belt tension, then retighten the nut and through bolt.
3. Recheck the tension of the belt.