4 — MAINTENANCE
4-15
4-6 TROUBLESHOOTING
Table 4-3. Troubleshooting Chart
Problem Cause Correction
1. Lift vehicle controls do not
work at upper or lower con-
trol box.
a. Master power switch turned off.
b. Low battery power or faulty battery
circuit.
c. Emergency stop button engaged
(pushed in).
d. Battery ground or in-series battery
cable loose.
e. Circuit breaker tripped.
f. Battery cable or equipment ground
lead loose or corroded.
a. Turn on master power switch.
b. Recharge batteries per paragraph 4-4.
Check for faulty battery or cables if
red battery charger LED is lit.
c. Rotate emergency stop buttons clock-
wise to disengage.
d. Check for and repair loose battery
connections or ground fault.
e. Reset breaker. If breaker trips again,
locate and correct short to ground in
power circuit wiring.
f. Clean and reconnect loose or cor-
roded battery cable or ground lead.
2. Lift vehicle controls do not
work at upper control box,
but do work at lower control
box.
a. Emergency stop button engaged
(pushed in) on upper control box.
b. Upper control box cable connectors
unplugged.
c. Upper control box cable connectors
plugged into wrong receptacles.
d. Enable pushbutton switch or wiring
faulty.
a. Rotate emergency stop buttons clock-
wise to disengage.
b. Plug in cable connectors at front of
upper control box.
c. Plug in cable connectors in opposite
receptacles at upper control box.
d. Repair wire break or replace faulty
switch.
3. When UP function is se-
lected, pump motor runs but
will not raise the platform.
a. Hydraulic oil level low in reservoir.
b. More than 500 lbs. on lift platform.
c. Emergency lowering valve open.
d. Up valve solenoid or solenoid wiring
faulty.
e. Down valve sticking open or leaking.
f. UP switch or UP switch wiring faulty.
g. Mast sections dirty; slide blocks
binding.
h. Internal leakage in hydraulic cylinder.
a. Check reservoir level. If low, check
for oil system leakage. Refill reservoir
and bleed air from hydraulic system
per instructions in paragraph 4-3.
b. Ensure load is 500 lbs. or less.
c. Close emergency lowering valve.
d. Check voltage at up valve solenoid. If
no voltage, check wiring. If voltage,
exchange solenoids and recheck func-
tion; replace solenoid if faulty.
e. Repair or replace down valve.
f. Check for lighted UP LED when up
switch is engaged. If LED does not
light, signal is not reaching main con-
troller; repair wire break or replace
faulty switch.
g. Clean and lubricate masts with dry
silicone. If needed, adjust slide bocks
per paragraph 4-5.
h. Check cylinder housing for heat
buildup due to leakage. If leakage is
indicated, repair or replace hydraulic
cylinder.
