Inspection And Testing Of Components; Removal Of Drive End Head View; Removal Of End Head Bearing View - Piper Navajo Chieftain PA-31-350 Service Manual

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Figure 11-7. Removal of Drive End Head
Figure 11-8. Removal of End Head Bearing
NOTE
The inner race of the slip ring end bearing is pressed onto the rotor
shaft. When bearing replacement is necessary, always replace the
complete bearing assembly, including the inner race.
f. To remove the drive end head from the rotor shaft, use a puller that grips on the bearing retainer
plate as shown in Figure 11-7. Do not attempt to remove by supporting the end head and pressing on the
shaft, as this may result in distortion of the end head or stripping of the retainer plate screws. Remove the
three retainer plate screws and press the bearing out of the end head. (Refer to Figure 11-8.)
11-13. INSPECTION AND TESTING OF COMPONENTS. Upon completion of the disassembly, all parts
should be cleaned and visually inspected for cracks, wear or distortion and any signs of overheating or
mechanical interference.
a. Rotor: The rotor should be tested for grounded or shorted windings. The ground test can be
made with test probes, connected in series with a 110 volt test lamp, an ohmmeter or any type of
continuity tester. (Refer to Figure 11-9.) There must not be any continuity between the slip rings and the
rotor shaft or poles. To test for shorted turns in the rotor winding, connect a voltmeter, ammeter and
rheostat as shown in Figure 11-10, or use an ohmmeter. Rotor current draw and resistance are listed in the
Alternator Service Test Specifications paragraph. Excessive current draw or a low ohmmeter reading
indicates shorted windings. No current draw or an infinite ohmmeter reading would indicate an open
winding.
b. Rectifiers: A diode rectifier tester will detect and pinpoint open or shorted rectifiers without
going through the operation of disconnecting the stator leads. However, if a tester is not available, test
probes and a No. 57 bulb, connected in series with a 12 volt battery, can be used in the following manner.
Touch one test probe to a rectifier heat sink and the other test probe to a lead from one of the rectifiers in
that heat sink. Then reverse the position of the leads. The test bulb should light in one direction and not
light in the other direction. If the test bulb lights in both directions, one or more of the rectifiers in that
heat sink is shorted. To pinpoint the defective rectifier, the stator leads must be disconnected and the above
test repeated on each rectifier. Open rectifiers can only be detected, when using the test bulb, by
disconnecting the stator leads. The test bulb will fail to light in either direction if the rectifier is open.
NAVAJO CHIEFTAIN SERVICE MANUAL
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