Section II. STARTER MOTOR - TM-10-3930-632-340053

TM 10-3930-632-34

KEY to figure 5-1:

The rotor may be checked electrically for

1. End frame

16.

Bearing

grounded, open, or short circuited field coils. To check

2. Bearing

17.

Retainer gasket

for grounds, connect a 110-volt test lamp or an

3. Bearing retainer

18.

Collar

ohmmeter from either slipring to the rotor shaft or to the

4. Capacitor

19.

Retainer plate

rotor poles. If the lamp lights, or if the ohmmeter reading

5. Ground terminal package

20.

Screw

is low, the field winding is grounded. To check for

6. Brush kit

21.

Stator

opens, connect the test lamp or ohmmeter to each

7. Brush spring

22.

Terminal

slipring. If the lamp fails to light, or if the ohmmeter

8. Screw

23.

Thru bolt

reading is high (infinite), the winding is open. The

9. Heat sink

24.

Terminal package

10.

Rotor

25.

Diode

winding is checked for short circuits by connecting a

11.

Nut

26.

Washer

battery and ammeter in series with the two sliprings.

12.

Lockwasher

27.

Screw

Note the ammeter reading (2.2 amps). An ammeter

13.

Drive end collar

28.

Heat sink

reading above the specified value indicates shorted

14.

End frame

29.

Terminal package

windings. An alternate method is to check the resistance

15.

Oil slinger

30.

Diode

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

during Reassembly.

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

end.

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

CAUTION

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

WARNING

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

5-5.

Repair

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.

5-4.

Cleaning and Inspection

5-6.

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

Reassembly sequence.

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

5-7.

General

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

5-3