TM 10-3950-206-12
80F., the reading for each cell of a fully charged battery
than 10*%.
should read between 1.260-1.275. If the specific gravity
(3) Install temperature sending units in re-
readings between the highest and lowest cells exceeds
verse of (1) above.
b. Engine Oil Pressure Sending Unit.
50 points (0.050), or the reading of the highest cell is
below 1.200, the life of the battery is questionable and
(1) Tag and disconnect the wire lead. Re-
should be replaced.
move the sending unit (6, fig. 4-13), elbow (7), and
(2) If the specific gravity readings are
adapter (8) as required.
approximately 1.170 per cell, indicating a half- charged
(2) Test the unit with electrical leads attached
battery, place the battery on charge until the specific
by connecting to a regulated air pressure source.
gravity approximates 1.260 per cell.
Replace unit if gage reading differs by more than 10%.
(3) The charging current rate for recharging
Caution: Do not use an air pressure
can be varied to conform to the time available for
source greater than 80 psi.
recharging:
(3) Install engine oil pressure sending unit in
(a) Fast charge; 40-50 amperes.
reverse of (1) above.
(b) Booster charge; 20-25 amperes.
c. Transmission Oil Pressure Sending Unit.
(c) Normal charge; 5-10 amperes.
(1) Tag and disconnect the wire lead. Remove
However, two conditions must be observed: the
the sending unit (14, fig. 4-13) and elbow (7).
temperature of the electrolyte must not exceed 125F.,
(2) Test unit same as paragraph b, (2) above.
and, the battery must be removed from charge after
(3) Install transmission oil pressure sending
three consecutive hourly specific gravity tests have read
unit in reverse of (1) above.
approximately 1.260.
d. Reverse Polarity Protector.
Caution: Do not use open flame near
(1) Tag and disconnect wire leads. Remove
the batteries while charging. The mixture of oxygen
two capscrews (5, fig. 4-13), nuts (1), lock- washers (2),
and polarity protector (9).
and hydrogen gases released during charging are
(2) Cleaning, Inspection, and Test.
highly flammable.
(a) Clean the exterior of the relay with a
(4) Refill the cells until the electrolyte level is
damp cloth and dry.
approximately 3/8 inch above the separator plates. Use
(b) Inspect the relay for cracked case
distilled water if electrolyte is not available.
and/or damaged connectors. Replace relay if damaged
Note. The specific gravity of the batteries
in any way.
should be checked biweekly. Continued usage of the
(c) Test the relay by connecting a 12 volt
batteries in a halfcharged condition will reduce their
battery to the relay with the positive battery terminal
normal life cycle. Normal operation of crane will keep
connected to the small connector on the re- lay and the
the batteries fully charged, but long periods of inactivity
negative battery terminal grounded to the relay case. A
or continued operation in high humidity may necessitate
discernable click should be noticed upon completing the
recharging.
circuit indicating a properly functioning relay. If no click
d. Installation. Install the batteries and cables in
is noticeable replace the relay.
the reverse order of instructions for removal. After
(3) Installation. Install the relay in reverse
securing cable clamps to battery, apply a light coating of
order of removal.
nonmetallic grease or petroleum jelly to battery terminals.
e. Starter Relay.
4-28. Sending Units and Miscellaneous Electrical
(1) Tag and disconnect wire leads. Remove
Components
three nuts (12, fig. 4-13) and lockwashers (11). Lift relay
a.
Temperature Sending Units.
The two
(10) from bracket.
temperature sending units (13, fig. 4-13) are thermo
(2) Install new relay in reverse of removal.
sensitive units for monitoring the temperature of the
4-29. Gages and Instruments
engine coolant and the transmission oil temperature.
a. Removal.
(1) Remove the units by disconnecting the
Warning: Before removing leads from
electrical lead and unscrewing the unit.
switches, gages, or senders, disconnect positive
(2) The units may be tested by reconnecting
the wire lead and comparing the gage reading with a
battery cable.
thermometer while suspending both in a heated pan of
water. Replace sending unit if temperature varies more
4-21
