Assembly Of Alternator; Testing Rotor For Ground View; Testing Rotor For Shorts View - Piper Navajo Chieftain PA-31-350 Service Manual

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RHEOSTAT
AMMETER
VOLTMETER
BATTERY
VOLTMETER
Figure 1 1-9. Testing Rotor for Ground Figure 11-10. Testing Rotor for Shorts
c. Stator: The stator can be tested for open or grounded windings with a 12 volt test bulb,
described in the rectifier section, or an ohmmeter, in the following manner. Separate the stator from the
slip ring end head just far enough to insert a fold of rags or blocks of wood. In other words, insulate the
stator from the end head. To test for grounded windings, touch one test bulb or ohmmeter probe to the
auxiliary terminal or any stator lead, and the other test bulb or ohmmeter probe to the stator frame. If the
test bulb lights, or the ohmmeter indicates continuity, the stator is grounded. To test for open windings,
connect one test probe to the auxiliary terminal or the stator winding center connection and touch each of
the three stator leads. The test bulb must light, or the ohmmeter must show continuity. Due to the low
resistance in the stator windings, shorted windings are almost impossible to locate. However, shorted stator
windings will usually cause the alternator to "growl" or be noisy during operation and will usually show
some signs of overheating. If all other electrical checks are normal and alternator fails to supply its rated
output, the stator should be replaced to determine whether or not it is the faulty component.
d. Bearings and Seals: Whenever the alternator is overhauled, new bearings and oil or grease seals
are recommended, even though the bearings and seals appear to be in good condition. A faulty seal can
cause an alternator to fail within a very short period of time.
11-14. ASSEMBLY OF ALTERNATOR.
a.
Press the ball bearing into the drive end head using a flat block approximately two inch square so
that the pressure is exerted on the outer race of the bearing. Install the retainer plate. With the snap ring
and retainer cup in place on the rotor shaft, use a tool that fits over the shaft and against the inner bearing
race, and press until the inner bearing race is against the snap ring retainer cup. (Refer to Figure 11-11.)
b.
Carefully install the rectifiers in the slip ring end head or rectifier mounting plate by supporting
the unit and using the special tools illustrated in Figure 11-12.
CAUTION
Use an arbor press, do not hammer. Reconnect the stator leads to
the rectifiers. When soldering these connections, use pliers as a
heat dam on the lead between the solder joint and the rectifier.
Too much heat will damage the rectifiers.
Reissued: 9/23/80 ELECTRICAL SYSTEM
NAVAJO CHIEFTAIN SERVICE MANUAL
3C24