SkyRider 15
4-8
Up Valve Operation Check
Refer to the hydraulic diagram in Figure 4-14. The normally-open Up valve routes oil
flow from the hydraulic pump to the reservoir. Pressing the
ENABLE and UP pushbuttons
energizes the Up valve. Oil flow to the reservoir is shut off, causing the lift cylinder to
extend. Releasing the
ENABLE or UP pushbutton causes the Up valve to open, routing all
hydraulic oil to the reservoir. Even if the hydraulic pump motor should continue to run,
the lift platform will not rise when the
ENABLE or UP pushbutton is released.
This fail-safe operation is defeated only if the Up valve sticks in the closed position. A
sticking valve and fused pump-start relay contacts would cause the lift platform to rise,
even after the
UP pushbutton is released. This would be an unsafe operating condition.
The following operation check indicates whether or not the Up valve is sticking:
1. Disconnect the lead wires from the Up valve solenoid, Figure 4-7.
2. At the lower control box, hold the key switch in the
LOWER CONTROL position
and press the
UP pushbutton. The hydraulic pump motor should run without rais-
ing the lift platform.
3. If the lift platform rises, the Up valve is sticking closed. Remove and clean or
replace the sticky valve.
4. Reconnect the lead wires to the Up valve solenoid.
Figure 4-7. Up Valve Operation Check
