Paccar CARCO 50B, Service Manual

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9
CONTROL SYSTEM OPERATION AND TROUBLESHOOTING
BASIC OPERATION
The winch contains an independent, internal hydraulic
system. The winch case serves as a reservoir and stores
filtered oil for the internally mounted hydraulic pump. The
pump is driven by a gear pressed onto the bevel pinion
gear, and supplies oil as long as the tractor PTO shaft is
turning. Oil from the pump is then routed through a pres-
sure filter then directed to the control valve where a
stand-by system pressure is maintained at 320-410 PSI
(2210-2830 kPa).
The system oil pressure is routed through the control
valve body to the solenoid actuated valve cartridges.
When energized by the electronic control system, the
solenoids direct oil to apply the Reel-In and Reel-Out
clutches, release the spring-applied brake and shift the
spring-engaged freespool mechanism. The electronic
winch control system includes a sealed, solid-state joy-
stick control lever and a sealed, solid-state control mod-
ule installed under the RH console of the tractor, an elec-
tric solenoid operated control valve installed within the
winch case, with a wiring harness connected between
them.
The hydraulic control system is equipped with an accu-
mulator. The spring-loaded accumulator stores a small
amount of oil at system pressure to assist the application
of the clutches and release of the brake under all operat-
ing conditions. The stored oil supply may also be used to
release the spring-applied brake whenever the tractor
engine or torque converter is stalled. The accumulator-
stored oil supply is continuously refilled by the pump and
pressure maintenance system in the control valve when-
ever the PTO shaft is turning.
On tractors that supply PTO power through a torque con-
verter, it is possible to cause the torque converter to stall
if the tractor engine speed is too low. It is important that
engine idle speeds be set to factory specifications to
maintain proper operation.
The solid-state joystick control lever has no contact points
to wear out or need adjustment, aside from the small
push-button switch on the top of the lever. This button
MUST be depressed to enable the electronic control sys-
tem to perform any winch function. This feature prevents
accidental or unwanted winch actuation.
The joystick produces a signal by a magnetically induced
voltage as the control lever is moved near the sensing
devices on the circuit board beneath the lever. The small,
induced voltage is transmitted to the control module
mounted beneath the console. The job of the control
module is to receive 24V DC power from the tractor, filter
this power supply to protect the electronics, then produce
the correct combination of 24V DC signals to energize the
appropriate solenoid cartridges in the control valve. The
control valve is mounted inside the winch case behind the
large access cover on the RH side. When energized by
the control module, the solenoids send control oil pres-
sure to perform the specific winch functions based on the
position of the joystick lever. An additional terminal built
into the winch end of the wiring harness allows for diag-
nostics and troubleshooting of electrical problems and
components. A small red indicator light, installed next to
the joystick, will illuminate to indicate that the hydraulic oil
filter is beginning to bypass and should be serviced if the
light remains on.
A small volume of oil is stored in the spring-type accumu-
lator at control system pressure. This stand-by pressure
ensures quick response to the operator's commands,
regardless of engine speed or winch load. The stand-by
pressure is maintained by the joint operation of a pres-
sure switch and a main pressure control solenoid valve.
The pressure switch will be closed and send current to
the main pressure solenoid until stand-by pressure reach-
es 370 PSI (2550 kPa). When the cutout pressure is
reached, the pressure switch de-energizes the solenoid
valve. The stand-by pressure is contained in the control
valve housing by a check valve, and slowly decreases to
315 PSI (2170 kPa), where it will close the pressure
switch contacts and start the charging process again.
When the operator selects a winch function, the pressure
switch is not used and the control module activates the
main pressure solenoid. A relief valve limits the main sys-
tem pressure to approximately 400 PSI (2760 kPa) during
clutch and brake actuation.
The wiring harness provides the vital connection between
the control module and the control valve. The connecting
pins and sockets are numbered for identification and trou-
ble-shooting. The pin and socket numbers are referenced
in the following descriptions of winch functions.