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 nine diodes, each diode must be tested for continuity in both directions with an ohmmeter that has diode checking capability; a total of 18 checks.
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.
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 Brush Inspection
1. Separate the drive-end housing from the rear housing as described .
2. Separate the rear housing from the stator/rectifier assembly by removing the four screws and the terminal nut from the rear housing.
3. Measure the length of the brushes with vernier calipers.
4. If the brushes are less than the service limit, replace them.
Alternator Belt Inspection and Adjustment
Deflection Method:
Apply a force of 98 N (10 kg, 22 lb), and measure the deflection between the alternator and the crankshaft pulley.
Deflection: 8.0 - 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 6.0 - 8.5 mm (0.26 - 0.33 in) when first measured. If the belt is worn or damaged, replace it.
If adjustment is necessary:
1. Loosen the lower mounting nut and the upper mounting bolt.
2. Move the alternator to obtain the proper belt tension, then retighten the upper mounting bolt and the lower mounting nut to the specified torques.
3. Recheck the deflection of the belt.
Belt Tension Gauge Method:
Following the gauge manufacturer's instructions, attach the special tool to the belt, and measure the tension.
Tension: 340 - 490 N (35 - 50 kg, 77 - 110 lb)
NOTE: On a brand-new belt (one that has been run for less than five minutes), the tension should be 540 - 740 N (55 - 75 kg, 121 - 165 lb) when first measured. If the belt is worn or damaged, replace it.
If adjustment is necessary:
1. Loosen the lower mounting nut and the upper mounting bolt.
2. Move the alternator to obtain the proper belt tension, then retighten the upper mounting bolt and the lower mounting nut to the specified torques.
3. Recheck the tension of the belt.