Piper COMANCHE PA-24-180 Service Manual page 556

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FIGURE 916. CROSS SECTIONAL VIEW OF ALTERNATOR
FIGURE 9.16. CROSS SECTIONAL VIEW OF ALTERNATOR
To remove the dnve end frame from the rotor, place the rotor in a vise and tighten only
enough to permit removal of the shaft nut.
CAUTION
Avoid excessive tightening as this may cause distortion of the
rotor. Remove the shaft nut, washer, pulley, fan, and the collar,
and then separate the drive end frame from the rotor shaft.
9-49. Checks.
a Rotor Checks - The rotor may be checked electrically for grounded, open, or short circuited
field coils. To check for grounds, connect a 110-volt test lamp or an ohmmeterfrom either slip
ring to the rotor shaft or to the rotor poles. If the lamp lights, or if the ohmmeter reading is low,
the field winding is grounded (Figure 917).
To check for opens, connect the test lamp or ohmmeter to each slip ring. If the lamp fails
to light. or if the ohmmeter reading is high (infinite), the winding is open (Figure 9-17).
The winding is checked for short-circuits by connecting
a battery and ammeter in series
with the edges of the two slip rings. Note the ammeter reading and refer to Delco-Remy Service
paragraph 9-57 for specifications. An ammeter reading above
the specified value indicates
shorted windings. An alternate method is to check the resistance of the field by connecting an
ohmmeter to the two slip rings (Figure 9-17). If the resistance reading is below the specified
value, the winding is shorted. The specified
resistance value can be determined by dividing the
voltage by the current given in paragraph 9-57.
If the rotor is not defective, and the alternator fails to supply rated output when checked
as covered in the section entitled Checking Alternator Output, the trouble is in the stator or
ELECTRICAL SYSTEM
ISSUED: /18/72
3 B10
PIPER COMANCHE SERVICE MANUAL