Section E - Hydraulics
Operation Description
Power Management System (P.M.S.)
E - 29 E - 29
9803-9450-2
The Power Management System (PMS) is designed to
reduce instances of engine stalling during operations
involving high transmission loads and to enhance
transmission control when operating attachments such as
patch planers.
The engine load is controlled by reducing the pump
displacement without fully unloading the transmission
pressure. The operator maintains full transmission control
but the automatic modulation of the control pressure
simulates an experienced operator backing off the
transmission control on encountering high resistance to
tractive effort such as a material pile.
PMS is permanently activated when the engine is running
and is controlled by Electronic Control Unit 4 (ECU 4). The
ECU is located above the rear section of the fuse panel.
ECU 4 is connected to terminal W on the alternator, the
PMS warning light B and the PMS dump valve C. On High
Flow machines only, the ECU is also connected to a
sensitivity control D.
Note: Electrical connections are indicated by blue (thin)
lines and hydraulic connections by orange (thick) lines
K
Fig 26. ( T E-28).
The PMS dump valve is positioned in the hydraulic feed
from the charge pump P4 to the transmission joy stick E.
Note: When a machine has dual transmission controls, the
output from PMS dump valve C feeds the transmission
spools of both joysticks.
Operation
When an increasing load causes engine speed to be
reduced, the frequency signal from the alternator W
terminal is sensed by ECU 4. The ECU then supplies a
corresponding signal to PMS dump valve C which in turn
reduces the pressure that is feeding joystick E.
This means that although the operator has moved the
joystick to full travel, the control pressure from the joystick
to the transmission is reduced. The swash angle is
therefore backed off, reducing the oil flow and
consequently reducing the tendency of the engine to stall.
On High Flow machines, the operator can control the
sensitivity of the PMS by turning knob D to a suitable
position between maximum (fully counter clockwise) and
minimum (fully clockwise). This has the effect of regulating
the control pressure supplied by the PMS dump valve for
any given engine speed.
During normal loading operations, knob D should be set at
maximum to allow the machine to operate at full speed.
Warning Light Indications
When the ignition is turned on the warning light B should
come on to indicate that the PMS is live. When the engine
is started the light should go off.
If a PMS fault occurs, light B may flash in the form of a blink
code K
Blink Codes ( T E-50).
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