The optional automatic level control uses a diverter valve to maintain the work tool in a level
position during the raising of the loader arms.
At machine start-up with the work tool control lever in HOLD, the charge pump sends oil
through the fan motor and the oil filter to the hydrostatic drive pump group.
From the hydrostatic drive pump group, charge oil is sent to the pilot shutoff valve solenoid
and to the lift, tilt, and auxiliary solenoids in the work tool control valve group. The energized
pilot shutoff valve solenoid enables pilot oil to be available at the work tool solenoid valves.
The pilot shutoff valve solenoid and the work tool solenoid valves are energized by the
Machine ECM.
When the auxiliary thumbswitch on the work tool joystick is activated or the work tool control
lever is moved from the HOLD position, a signal is sent to the Machine ECM. The Machine
ECM sends a corresponding signal to energize a solenoid, which directs pilot oil to the
appropriate control valve spool in the control valve group. The more the thumbswitch or work
tool control lever is moved, the higher the pilot oil flow that is directed to the work tool control
valve spool.
The amount of pilot oil to the work tool control valve group determines the distance the spool
in the control valve shifts and the amount of hydraulic oil directed to the cylinders from the
pump.
The tilt circuit is equipped with line relief valves for the rod and head ends of the cylinder. The
lift circuit is equipped with a line relief valve and a manual lowering valve on the head end of
the lift cylinder circuit.
The auxiliary circuit is equipped with a line relief valve for the two auxiliary lines.
With all the control valve group valves in HOLD (shown), the pump supply oil flows through
the center passage of each valve before returning to the tank. When in HOLD, a centering
spring keeps the control spool centered. Pump supply oil enters the supply passages, flows
around the control spool, and flows to the next valve. Supply oil also flows to the load check
valve.
SERV1833-01 - 77 - Text Reference
07/08