Fan
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| Illustration 1 | g00479665 |
Alternator Rotor With Attached Fans | |
The G3B, K3A, and L3A alternators have two internal fans. The fans are connected to the rotating shaft. Check for deformed, missing fan blades.
Ball Bearing
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| Illustration 2 | g00479670 |
(1) Front Bearing Of The Alternator | |
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| Illustration 3 | g00479672 |
(2) Rear Bearing Of The Alternator | |
Rotate the bearing by hand and check for resistance or noise. Replace the bearing if problems are detected.
Stator
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| Illustration 4 | g00479676 |
(3) Lead Wires Of The Stator | |
Check the resistance that is between each of the phases. Measure the resistance between the end of each lead wire and neutral point. The resistance should be less than 1 ohm.
Measure the insulation resistance between the core and the coil. Use the 142-5055 Insulation Tester Group . Set the insulation tester at 500V. The resistance should be more than 100000 ohms. When there is no continuity, check the lead wire connection. Disconnection of the stator coil is unlikely.
Rotor
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| Illustration 5 | g00479720 |
Alternator Rotor And Slip Rings (4,5) . | |
Check the resistance between slip rings (4) and (5) . See illustration 5. The resistance should measure approximately 2.9 ohms for 12 volt alternators. The resistance should measure approximately 12 ohms for 24 volt alternators.
Check the insulation resistance between each slip ring and the pole core. Use the 142-5055 Insulation Tester Group . The resistance should be more than 100000 ohms.
Check for stains or roughness on the surface of the rotor. Use fine sandpaper (300 grit to 500 grit) to remove roughness. A slip ring is usable until the outer diameter wears from 14.4 mm (0.5669 inch) to 14 mm (0.5512 inch) .
Rectifier
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| Illustration 6 | g00479742 |
Rectifier With Lead Terminals (6) And B Terminal (7) | |
Check the continuity of the rectifier. Use the kilohms scale of the multimeter. Do not use the 142-5055 Insulation Tester Group . The rectifier would be destroyed.
In order to check the positive diodes, place one lead of the multimeter on one of the terminals (6) . Place the other lead of the multimeter on the B terminal (7) . Measure the continuity. Reverse the positions of the leads and measure the continuity again. The proper functioning of the positive diode is demonstrated by the difference in resistance when switching the positions of the multimeter leads. The difference must be great. The difference indicates that the diodes of the rectifier are functioning. Repeat the process for the remaining three terminals (6) .
If the multimeter has a option to check diodes on the selector, the readings are more accurate.
The diode is functioning properly when the leads are connected one way and the multimeter shows "0L". Then, the multimeter shows approximately .5 volts when the lead connections are reversed.
The diode is shorted when the leads are connected one way and the multimeter shows "00". Then, the multimeter shows "00" when the lead connections are reversed.
The diode is open when the leads are connected one way and the multimeter shows "0L". Then, the multimeter shows "0L" when the lead connections are reversed.
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| Illustration 7 | g00519782 |
Rectifier With Negative Diode Contacts (8) And Positive Diode Contacts (6) | |
To check the negative diodes, place one lead of the multimeter on any one of the negative diode contacts (8) . Connect the other lead of the multimeter to one of the terminals (6) . Measure the continuity in the previous manner. Repeat the process for the remaining three terminals (6) . The expected results are identical to the results for the positive diodes.
Brush
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| Illustration 8 | g00479747 |
Brush For 55 Ampere Alternator | |
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| Illustration 9 | g00479751 |
Measure the protruded brush length. Compare the measurement to the value that is listed in Specifications. Replace worn out brushes.
Regulator
| NOTICE |
|---|
The check should be done in the following sequence. If the check is done in the wrong sequence, the IC regulator would be put into the wrong function and a correct check could not be done. If the check is started with the circuit not connected properly, turn off the electric source at once. Then start the check again in the proper sequence. |
- Connect the components so that the circuit that is shown in illustration 10 is formed. Keep "SW1" and "SW2" in the OFF position.
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| Illustration 10 | g00524708 |
Schematic For 12 Volt IC Regulator Test "L1" is a substitute for the charge indicator. "L2" is a substitute for the rotor coil. | |
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| Illustration 11 | g00520471 |
Schematic For 24 Volt IC Regulator Test "L1" is a substitute for the charge indicator. "L2" is a substitute for the rotor coil. | |
Note: The "E" terminal is NOT the fin. The arrow is pointing to a terminal in that location on the back side of the regulator. The "E" terminal connects to the alternator frame.
- Adjust the source voltage to 12 volts. For a 24 volt alternator, adjust the source voltage to 24 volts. Values for both alternators are given in the following procedure.
- Turn ON "SW1", and check if "L1" is lighted brightly. "L1" is the substitute for the charge indicator. "L2" should be lighted dimly. "L2" is the substitute for the rotor coil.
- Turn ON "SW2" while "SW1" is still turned on. Check that "L1" turns OFF, and check that "L2" and "L3" are lighted brightly.
- Keep "SW1" and "SW2" in the ON position, and gradually raise the voltage of the variable DC power source. Raise the voltage from 12 volts, and check that the "L2" lamp is turned OFF at a voltage of 14.2 ± 0.6 volts at 25 °C. "L1" remains OFF. For 24 volts alternators, raise the voltage from 24 volts. The "L2" lamp is turned OFF at a voltage of 28.0 ± 1.0 volts at 25 °C.
- Reduce the source voltage to 12 volts (24 volts) and check if the "L1" lamp is turned ON. "L2" should turn on.