KEY to figure 5-1:
The rotor may be checked electrically for
1. End frame
grounded, open, or short circuited field coils. To check
for grounds, connect a 110-volt test lamp or an
3. Bearing retainer
ohmmeter from either slipring to the rotor shaft or to the
rotor poles. If the lamp lights, or if the ohmmeter reading
5. Ground terminal package
is low, the field winding is grounded. To check for
6. Brush kit
opens, connect the test lamp or ohmmeter to each
7. Brush spring
slipring. If the lamp fails to light, or if the ohmmeter
reading is high (infinite), the winding is open. The
9. Heat sink
winding is checked for short circuits by connecting a
battery and ammeter in series with the two sliprings.
Note the ammeter reading (2.2 amps). An ammeter
Drive end collar
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
sliprings. If the resistance reading is below the specified
Separate the drive end frame (14, fig. 5-1)
value, the winding is shorted. The specified resistance
and roter assembly (10) from the stator assembly (21) by
value can be determined by dividing the voltage by the
prying apart with a screwdriver at the stator slot. A
current (14 + 2.2 5 to 7 ohms).
scribe mark will help locate parts in the same position
To check the stator windings, remove all three
stator lead attaching nuts and then separate the stator
Following disassembly, place a piece of tape
assembly from the end frame. The fit between stator
over the slipring end frame bearing (2) to prevent entry of
frame and end frame is not tight, and the two can be
dirt. Place a piece of tape over the shaft on the slipring
separated easily. The stator windings may be checked
with a 110-volt test lamp or an ohmmeter. If the lamp
To remove the drive end frame (14) from rotor
lights, or if the meter reading is low when connected from
(10), place the rotor in a vise and tighten only enough to
any stator lead to the frame, the windings are grounded.
permit removal of the shaft nut.
If the lamp fails to light, or if meter reading is high when
successively connected between each pair of stator
leads, the windings are open. A short circuit in the stator
Avoid excessive tightening as this may cause
windings is difficult to locate without laboratory test
distortion of the rotor.
equipment due to the low resistance of the windings.
However, if all other electrical checks are normal and the
generator fails to supply rated output, shorted stator
Dry cleaning solvent, P-D-680, used to clean
windings are indicated.
parts is potentially dangerous to personnel and
property. Avoid repeated and prolonged skin
contact. Do not use near open flame or
excessive heat. Flash point of solvent is 100°
Repair consists of replacement of all parts found to
F. - 138° F. (39° C. - 59° C.).
be unserviceable during inspection or testing.
Cleaning and Inspection
Reassembly and Installation
Wipe all parts of the alternator, except the
Reassemble the alternator as shown in figure
brushes, with a cloth dampened in cleaning solvent P-D-
5-1. Reverse order of indexing depicted therein for
680. Dry thoroughly with low pressure, dry, compressed
air. Wipe the brushes with a clean, dry cloth.
Install the alternator (TM 10-3930-632-12).
Inspect ball bearing (16, fig. 5-1) for cracked,
pitted balls and wear.
Check the size of the brushes. Replace if less
than one-half size of new brushes.
Section II. STARTER MOTOR
turned to the start position, and the transmission is in
neutral, the circuit to the starting relay closes. The relay
closes a circuit through the solenoid switch, which, when
A 12-volt battery provides the power necessary to
energized, engages the pinion on the starter drive
operate the engine starter. When the starting switch is