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Component - Test
SMCS - 1405-081

Fan

Illustration 1
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Alternator Rotor With Attached FansThe 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
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(1)Front Bearing Of The Alternator

Illustration 3
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(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

Illustration 4
(3) Lead Wires Of The Stator

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Check the resistance that is between each of the phases. Measure the resistance between the end of each lead wire
andneutral 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.

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Illustration 5
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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. Theresistance 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 outerdiameter wears from 14.4 mm (0.5669 inch) to 14 mm (0.5512 inch) .

Rectifier

Illustration 6
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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 multimeteron 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 thediodes 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.
Thediode is shorted when the leads are connected one way and the multimeter shows "00". Then, the multimeter

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shows "00" when the lead connections are reversed.
The diode is open when the leads are...