Motor Brush Replacement

TM 10-3930-609-12

commercial practice in their repair. Refer to the

level of electrolyte is 1/4 inch from bottom of

wiring diagram (fig. 1-3) and conduct a syste-

filler neck.

matic inspection using an ohmmeter to isolate

Caution: Do not use water which has passed

the trouble. Remedy the trouble by splicing

through a water softener. This water is chemic-

leads where required and applying electrical tape

ally destructive to a lead-acid battery. It is not

to prevent short circuits from occurring. Refer to

equivalent to distilled water.

direct support maintenance for replacement of a

complete wiring harness or repair to wiring en-

(1) Add water slowly. Water should be

cased in flexible metal conduit.

added before charging to insure prompt mixing

with the electrolyte.

(2) In sub-freezing temperatues battery

3-48. Motor Brush Replacement

must be put on finish charge for one hour after

Motor brush replacement (fig. 3-16) for the

water has been added.

travel motor or hydraulic pump motor is the

d. Cleaning the Battery. The entire battery

same.

and battery compartment should be kept clean

a. Removal.

and dry. If the electrolyte has been spilled or

(1) Remove screw, nut and lockwasher

corrosion has formed on the battery proceed as

securing brush covers to motor housing and re-

follows:

move brush covers.

(1) Add one pound of bicarbonate of soda

(2) Remove screw and lockwasher securing

to one gallon of warm water. Pour solution over

brush leads.

corrosion or spilled electrolyte.

(3) Pull back on brush spring sufficiently

(2) When foaming action stops rinse off

to release brush and pull brush out of brush

the entire battery with clear water.

holder.

Caution: Vent plugs must be installed in

(4) Repeat steps (1) through (3) for re-

moval of remaining brushes.

cells to prevent soda solution from getting into

b. Inspection. Compare length of used brush

the cells. Do not use steam or very hot water to

with length of a new brush from stock. Replace

clean battery.

any brush worn to half (or less) the length of

e. Charging the Battery. Batteries normally

new brush, as given below.

discharged more than one third of their capacity

c. Installation.

daily should be recharged daily. Other batteries

(1) Install new brushes in brush holders

in use should be charged at least once a week.

with short side of brush toward spring side of

Do not charge batteries more often than neces-

holder, so brush friction surface contour mates

sary to reduce gassing and water loss. Plan on re-

with surface of armature commutator. If brush

charge time, for a completely discharged battery,

edge meets commutator, reverse brush in hold-

of about eight hours, proportionally less for

er. Fasten brush leads to holder with removed

partially discharged batteries. Charge as follows:

screws and lockwashers.

(1) Disconnect battery leads at battery con-

(2) Hook brush springs over brushes and

nector receptacle and connect charger to battery

check pressure exerted on brush with brush

half of connector.

spring pull scale. Pressure should be 26 ounces

(2) Using procedure appropriate to the

to 32 ounces at time scale lifts spring from brush

charger being used, adjusted initial charging

on either motor.

rate for a fully discharged battery of 130 to 160

(3) Install brush covers and secure in posi-

amperes.

tion on motor housing with removed screw, nut

(3) At end of charging time disconnect

and lockwasher.

charger and observe cell vent; caps for signs of

excessive gassing. This is usually indicated by

3-49. Relay Contact Replacement

electrolyte around the fill hole of the cell.

Relay contact maintenance is restricted to those

f. Removal. Reverse the procedures outlined

relays having contacts visible for inspection, and

in paragraph 2-4e.

replaceable without removing the relays. Main-

g. Installation. Refer to paragraph 2-4e.

tenance requiring more than contact or interlock

switch replacement, shall be performed by direct

3-47. Wiring Harness

support maintenance personnel. Contacts require

Repair of the wiring harness is limited to iso-

replacement when the silver has worn down to

lating shorted and open circuits and using good

the steel support.

3-23