TM 5-3805-262-20
1-21. ELECTRICAL SYSTEM (CONT)
4. RETURN-TO-DIG CIRCUIT.
Return-to-dig circuit returns bucket to digging position
after it has been dumped. It includes a micro switch mounted on return-to-dig con-
trol rod located on right bucket tilt cylinder and an actuating rod inserted in con-
trol rod and connected to rod end of tilt cylinder. Micro switch is connected to
solenoid located on hydraulic control valve in tilt spool. With bucket raised and in
dump position, micro switch and solenoid are deenergized. Placing LIFT ARM control
lever in FLOAT and BUCKET control lever to CROWD will cause bucket to lower to
ground.. At same time, bucket will roll back until actuating rod actuates micro
switch arm in turn energizing solenoid in tilt spool. With tilt spool solenoid ener -
gized, BUCKET control lever will return to its NEUT. position stopping roll back of
bucket.
5. BUCKET HEIGHT CIRCUIT.
Automatically stops loader lift arms at an operator
selected dump height. It includes a micro switch mounted to height control bracket
located on left side of loader. Micro switch is connected to solenoid located on hy-
draulic control valve in lift spool. Micro switch actuated when loader lift arms
reach preset height energizing solenoid,
in turn, causing lift spool to return to
neutral position. This stops loader lift arms from raising any further.
6. AUXILIARY STEERING.
Consists of steering motor and pump, flow switch mounted in
hydraulic system, relay socket assembly, and warning buzzer and indicator.
Auxiliary Steering Motor and Pump.
Electrically operated motor with hydraulic oil
pump mounted on output shaft. Installed on left of rear chassis near transmission .
Automatically operates when hydraulic oil flow stops through hose in which flow
s w i t c h i s i n s t a l l e d.
Flow Switch.
Mounted in hose connected to hydraulic oil cooler. When hydraulic pump
mounted on transmission is operating, flow switch provides dc voltage to relay A,
pin 2 (figure FO-3). When hydraulic oil flow through hose stops, flow switch routes
dc voltage to relay A, pin 6.
Relay Socket Assembly (Figure FO-3).
Contains control circuitry for turning on aux-
iliary steering motor and pump. Mounted at side of front chassis. Relay A is connec-
ted as a latching relay. 24 Vdc applied to relay A coil at pin 2 energizes relay A.
24 Vdc applied to pin 1 and switched out pin 3 latches relay A coil on. Relay A, pin
6 switched to pin 8 has no effect on the circuit. When hydraulic oil flow stops
either due to engine, transmission, or hydraulic pump failure,
flow switch routes dc
voltage to relay A, pin 6. This voltage is switched out pin 8 and applied through 47
ohm resistor to relay B, pin 2 and 2000 microfarad capacitor. 2000 microfarad
capacitor and 47 ohm resistor provide a small time delay before relay B coil
e n e r g i z e s.
When relay B coil energizes, 24 Vdc at pins 1 and 3 latch relay B coil
and 24 Vdc at pins 6 and 8 sounds buzzer,
turns on indicator, and energizes
auxiliary steering motor solenoid turning on motor. With motor operating, hydraulic
pump attached to its output shaft starts oil flow through hoses. Flow switch will
switch 24 Vdc from one contact to the other , which has no effect on circuit due to
relays being latched. Auxiliary steering motor and pump will continue to operate
until ignition key switch is placed in off position. When ignition key switch is
placed to off position, 2000 microfarad capacitor will discharge through 50 ohm
r e s i s t o r a n d d i o d e.
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