JLG 450A_AJ Series II Service Manual - Manual (Page 99)

SECTION 3 - CHASSIS & TURNTABLE
3121180 – JLG Lift – 3-49
Troubleshooting
Table 3-3. 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 system 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 cou-
plings. 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 align-
ment. 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 3-4. 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 operating 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 3-5. 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 sig-
nal 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 orifices are properly
installed and not
obstructed.
Supply and drain orifices determine motor shift rate. The
smaller the orifice, 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.