Testing

TM 10-3930-621-34

Install brush holders (6), brushes (5) on

5-13. Testing

commutator end frame (38). Place end frame on field

a. Armature.

frame and connect ungrounded brush leads to field coil

(1) Place armature on "growler" and with a steel

terminals.

strip or hack saw blade held on armature core, rotate

d. Install bearing assembly (23) on armature shaft

armature. If blade vibrates, armature is shorted in area

(17) with long side towards commutator end of armature.

of the core below the vibrating blade. Eliminate short by

e. Install key (18) in armature shaft and press on

either cleaning out slots or bending shorting wire slightly

drive mechanism. Apply thin coating of grease before

and reinsulating it.

If short cannot be eliminated

pressing on drive assembly.

armature should be replaced.

Note. If drive assembly is rotated to a fully

(2) Place one probe of test lamp on armature core

extended lock position on screw shaft during

or shaft and place other probe on each commutator bar

replacement or during overhaul of cranking motor, do not

in turn. If lamp lights, armature is' grounded and should

attempt to force it in the reverse direction. Proceed to

be replaced.

install drive even though it is fully extended. After starter

b. Coils.

motor is installed on engine and the engine starts,

(1) Using a test lamp, place probes on each of the

centrifugal force will disengage drive pinion from flywheel

field leads of starter motor. If lamp does not light, coils

ring gear in the usual manner.

are open and starting motor must be replaced.

f. Place drive end housing (24) on armature shaft

(2) Place one probe of test lamp on field frame and

after placing a few drops of oil on bushing (28). Fasten

other probe on a field coil lead. If test lamp lights, starter

center bearing on drive housing.

motor terminal or one of field coils forming a pair are

Place washer (13) on commutator end of

grounded, and starting motor must be replaced.

armature shaft and install armature complete with drive

c. Brush Holder. Using test lamp, place probe on

housing in field frame assembly. While in- stalling

each of insulated brush holders in turn and other lead on

armature, pull commutator end frame away from field

commutator end frame. If lamp lights, brush holder is

frame and make certain brushes are seated correctly on

grounded due to defective insulation.

commutator.

5-14. Assembly

h. Replace end frame and position drive end

a. Refer to figure 5-5 for referenced item numbers.

housing on field frame. Make certain both commutator

b. Secure cranking motor in bench vise and slide

end frame and drive housing are correctly positioned on

armature

(17)

into

field

coil

housing.

field frame dowels. Then insert the thru-bolts and tighten

securely.

5-15. Installation

Refer to TM 10-3930-621-12 for starter motor installation

procedures.

Section III. RADIATOR

inside the counterweight and is protected b)y a grille

5-16. Description.

mounted in the back of the counterweight. A power shift

a. The engine cooling system consists of the water

transmission oil cooler is an integral part of the bottom

pump, radiator, thermostat, cooling fan, water passages

tank of the radiator to prevent overheating of the

in the cylinder block and head, and necessary hoses and

transmission oil.

lines to complete the system.

d. The thermostat, located at the top of the water

b. The water pump draws water from the bottom of

,pump housing, operates automatically to) maintain a

the radiator and circulates it through the water passages

normal operating temperature of approximately 165" F.

in the engine. It then passes from the cylinder head of

5-17. Removal

the engine through the thermostat and the upper radiator

hose, to the upper part of the radiator. The water is

Refer to TM 10-3930-621-12 for raditor removal

cooled as it passes from the top to the bottom of the

procedures and figure 5-6.

radiator by air drawn through the radiator core by the

5-18. Inspection and Repair

cooling fan.

a. Clean air passages in core- and test for leaks as

c. The radiator core is of the conventional tubular

follows:

type consisting of an upper and lower tank and side

members. It is mounted to the truck frame

5-7