General
The hydraulic system provides the force required to
lift the loads on all motorized lift trucks.
The hydraulic system on the motorized lift truck
consists of the following individual components:
• Pump Motor Assembly
• Hydraulic Pump Assembly
• Solenoid Lowering Valve
• Pilot Relief Valve
• Lift Cylinder
• Reservoir
The hydraulic pump and motor assemblies are
mechanically joined together as a compact unit,
combining the reservoir, pump, and motor together as
a single assembly. The pump is located inside of the
hydraulic tank and coupled to the motor by an adapter
plate, coupler drive, and four capscrews.
Hydraulic unit servicing is best performed by
removing the unit from the truck to a clean work area.
Special Precautions
WARNING
The capacitor in the transistor controller can hold
an electrical charge after the battery is disconnec-
ted. To prevent electrical shock and personal in-
jury, discharge the capacitor before inspecting or
repairing any component. Wear safety glasses.
Make certain the battery has been disconnected.
DO NOT use a screwdriver to discharge the trac-
tion motor controller.
WARNING
To avoid personal injury and prevent electrical
shock, perform the following steps before per-
forming any troubleshooting or adjustments, and
connecting or disconnecting a handset or PC.
CAUTION
To avoid controller damage, always disconnect
the battery. Discharge the capacitor and never put
power to the controller with any power wire dis-
connected.
Never short any controller terminal or motor ter-
minal to battery. Make sure to use proper proce-
dures when servicing the controller.
1. Move the truck to a safe, level area. Turn the key
switch to the OFF position and disconnect the
battery.
2. Remove the drive unit compartment cover to ac-
cess the drive unit compartment.
CAUTION
DO NOT short across the motor controller termi-
nals with a screwdriver or jumper wire.
3. Discharge the capacitors in the controllers by con-
necting a 200-ohm, 2-watt resistor across the
controller's B+ and B− terminals. See Figure 1.
4. Remove the 200-ohm, 2-watt resistor before re-
connecting the battery.
1900 YRM 1506 General
1
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