Piper Navajo PA-31 Service Manual page 703

PIPER NAVAJO SERVICE MANUAL
11-11. DISASSEMBLY OF ALTERNATOR.
After extended periods
of operation,
or at time of engine overhaul,
the alternator
may be removed for a thorough
inspection and cleaning of all parts.
The alternator
consists of four main com-
ponents - the two end frames,
the stator, and the rotor.
To disassemble
the alternator, take out the four thru-bolts
and separate
the drive end frame
and rotor assembly from the stator
assembly
by prying
apart with a screwdriver
at the stator slot. A mark will help locate
the parts
in the same position during assembly.
The fit between stator and frame is not
tight and the two can be separated
easily. Note that the separation
is to be made
between the stator
frame and drive end frame.
After disassembly, place a piece
of tape over the slip ring end frame
bearing on both sides to prevent
entry of
dirt and other foreign
material,
and also place a piece of tape over the shaft on
the ring end. If brushes are to be re-used,
clean with a soft, dry cloth.
CAUTION
Do not use black friction tape. Use only pressure
sen-
sitive tape that will not leave any contamination
on the
shaft surface.
To remove the drive 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 distor-
tion. Remove the shaft nut, washer,
pulley, fan and
collar, and then separate
the drive end frame from
the rotor shaft.
Additional disassembly
procedures are covered in the following sections.
11-12. CHECKS.
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 ohmmeter from 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.
(Refer to Figure 11-4.)
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 wind-
ing is open. (Refer to Figure 11-4.)
Reissued: 10/12/79 ELECTRICAL SYSTEM
Effectivity
DELCO
4B1