Oshkosh Corporation JLG 450AJ, Service And Maintenance Manual

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SECTION 3 - CHASSIS & TURNTABLE
3121659 – JLG Lift – 3-21
Troubleshooting
Table 3-2. Excessive Noise and/or Vibration
Item Description Action
Check oil level in reservoir and oil
supply to motor. Insufficient hydraulic fluid could lead to cavitation that would cause sys-
tem noise. Fill reservoir to proper level and ensure oil supply to motor is adequate and
lines are unobstructed.
Check for air in system. Air trapped in system lines or motor could result in cavitation that would
cause system noise. Ensure system lines and components are purged of air.
Inspect output shaft couplings. A loose or incorrect shaft coupling will produce vibrations that could result
in system noise. Ensure correct coupling is used and fits properly on shaft.
Inspect output shaft alignment. Misaligned shafts create excessive frictional vibration that could result in
system noise. Ensure that the shafts are properly aligned.
Hydraulic oil viscosity above limits. Viscosity above acceptable limits will result in cavitation that would lead
to system noise.
Replace hydraulic oil with appropriate fluid for operating conditions.
Table 3-3. System Operating Hot
Item Description Action
Check oil level in reservoir and oil
supply to pump. Insufficient amount of hydraulic fluid will not meet system cooling
demands. Fill reservoir to proper level.
Inspect heat exchanger
(if equipped). If heat exchanger fails or becomes obstructed, it may not meet system
cooling demands. Ensure heat exchanger is receiving adequate air flow and is in good operat-
ing condition. Repair or replace as necessary.
Check system relief valves. If a system relief valve becomes unseated for an extended period of time or
fails for any other reason, the system could become overheated. Repair or replace any malfunctioning relief valves and verify loads on
machine are not excessive.
Table 3-4. Won’t Shift or Slow to Start
Item Description Action
Check signal line to servo control
port. Obstructed or restricted flow through the servo control signal lines could
result in slow shift or no shift conditions within the motor. Ensure signal lines are not obstructed or restricted and that signal pressure
is adequate to shift the motor.
Check correct supply and drain ori-
fices are properly installed and not
obstructed. Supply and drain orifices determine motor shift rate. The smaller the ori-
fice, the longer time it takes to shift the motor. Obstruction also increases
shift times. Ensure proper control orifices are installed in motor and check they are not
obstructed. Clean or replace as needed.