Radio Interference Suppression

TM 5-4320-234-34

(7) Use a growler to test the armature for

following the sequence indicated in figure 3-15. Note

shorted windings. Shorts can sometimes be corrected

the following.

by removing metal particles imbedded between

(1) If you have already removed the brushes,

commutator bars. Replace armature if short cannot be

be sure to remove screw (1) and lock washer (2) to

located and corrected.

disconnect the field coil connections from the solenoid

(8) Use a 110-volt test lamp and check for

motor terminal.

continuity between adjacent commutator bars.

(2) Before removing the pinion drive

continuity does not exist, then the armature windings are

assembly (35), you must remove the retainer (33). To

open.

Check for loose connections between the

do this, slide a metal cylinder on the shaft that will make

conductors and the commutator. Poor connections will

contact with the retainer edge only. Drive the retainer

cause arcing and burning of the commutator.

toward the armature core and off the snap ring (32).

(9) Use the test lamp to check for continuity

Remove the snap ring from the groove in the armature

between commutator bars and armature shaft.

shaft and continue disassembly.

continuity exists between commutator bars and

(3) Do not remove the sleeve bearing (30)

armature shaft, the armature windings are grounded.

from the pinion housing (29) unless inspection indicates

Replace a grounded armature.

bearing is damaged.

(10) Inspect the field coil windings in the frame

(4) Do not disassemble the field coils (45 and

for damaged insulation, broken wires, and damaged

47) from frame unless tests indicate they are damaged

terminals. Revarnish damaged insulation. Replace

and must be replaced.

frame and field assembly if badly damaged.

f. Cleaning and Inspection.

(11) Disconnect the field coil ground

(1) Discard and replace gasket and oil seal.

connections and, using the test lamp, check for grounds

WARNING

between each winding lead and frame. Check for open

Clean all parts in a well-ventilated

windings by connecting test lamp probes to the winding

area. Avoid inhalation of solvent

leads. Continuity must exist. Replace field windings

fumes and prolonged exposure of

that are open or grounded.

skin to cleaning solvent. Wash

(12) Inspect the pinion housing sleeve bearing

exposed skin thoroughly.

Dry

for scoring and wear. Press a damaged bearing from

cleaning solvent (fed. spec. P-D-

the housing, and press a new bearing into the housing.

680) used to clean parts is

g. Reassembly. Reassembly is essentially the reverse

potentially

dangerous

procedure of disassembly refer to figure 3-15. Pay

personnel and property. Do not

particular attention to the following:

use near open flame or excessive

(1) After you install the drive assembly (35)

heat. Flash point of solvent is 100

and bearing (34) onto the armature shaft, place the

to 138 F (38 to 59 C).

retainer (33) onto the shaft with the cupped surface

CAUTION

facing the snap ring groove. Place the snap ring (32)

Saturating electrical parts with

onto the shaft. Force the snap ring over the shaft end

cleaning solvent will damage

by placing a block of wood on it and lightly tapping with

them.

a hammer. Slide the ring into the groove. To force the

(2) Clean the solenoid switch, armature, field

retainer over the snap ring, place a suitable washer over

frame and coil assembly, and drive assembly with a

the shaft, and squeeze retainer and washer together

cloth dampened lightly in cleaning solvent (fed. spec.

with pliers. Remove the washer and install the collar

P-D-680). Blow dry with clean, dry compressed air.

(31).

(3) Clean all other metal parts thoroughly in

(2) After you install the solenoid, apply a

cleaning solvent. Dry thoroughly with compressed air.

sealing compound between the field frame, flange and

(4) If necessary, you may clean the armature

solenoid junction.

commutator with No. 00 sandpaper. Do not use emery

h. Installation. Install the starting motor (TM 5-4320-

cloth.

234-12, para 4-42).

(5) Inspect the brushes as directed in

3-20. Radio Interference Suppression

subparagraph c above.

a. Description. Essentially, suppression is attained by

(6) Inspect the armature for damaged

providing a low resistance path to ground for stray

insulation, worn or out-of-round commutator, and

currents. The methods used include shielding the

damaged bearing surfaces on shaft.

Revarnish

ignition and high frequency wires and grounding the

damaged insulation, allowing the varnish to soak into

frame with bonding straps.

the windings.

You can smooth damaged bearing

surfaces with crocus cloth.

Replace armature if

b. Replacement of Suppression Components. This

damaged beyond repair.

equipment uses no primary radio suppression com-

3-19