6.ALTERNATOR INSPECTION, ASSEMBLY AND INSTALLATION In order to prevent the output voltage of the alternator from increasing beyond the specified limit, an electronic integrated circuit regulator is used. The setting of the regulator is non-adjustable. The regulator unit also carries the brushes. The alternator provides alternating current that is converted to direct current by rectifiers and then used for battery charging.
6.0
Objectives After going through this lesson, you will be able to: Inspect components of the alternator viz. rotor, stator, rectifiers, diodes and brushes Assemble the alternator. Install the alternator in the car.
i. ii. iii.
6.1
Inspection of Rotor First touch the test probes together and check the multimeter for proper working.
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6.2 窶｢
6.3
Touch the test probes of the multimeter to the slip rings to check the rotor for continuity. The resistance shown should be between 3.4 to 3.7 ohms. If there is no continuity, the field coil is open窶田ircuited and must be replaced. Touch the test probes of the multimeter on each slip ring and the rotor to check the rotor for grounding. There should be no continuity. Presence of any continuity indicates that the insulation on the field coil has failed, making the replacement of the rotor necessary.
Inspection of Stator Touch the test probes of the multimeter on the stator core and on each coil lead one after the other. If continuity is detected, the stator should be replaced.
Inspection of Rectifiers
The positive rectifiers are checked first. The rectifiers are considered to be acceptable if continuity is present when the positive test probe, which is red in color, is touched to positive side heat sink and the negative test probe is touched to the rectifier lead. At the same time, continuity should be absent when the test probes are reversed. All the three rectifiers are checked in a similar manner.