Stellar
®
Heavy-Duty Telescopic Crane Owner’s Manual | Page 29
proportional valve.
• Check to see if the manual override on the proportional valve is turned out. Turn the
manual override on the flow valve in (7621 thru 12630 models only).
Problem: Crane operates slowly.
Solutions:
• Make sure that the crane is receiving the recommended hydraulic flow to operate.
• Check the level of hydraulic fluid in the reservoir. Add fluid as needed.
• Check hydraulic fluid temperature.
• Check to see if the valve bank orifice is plugged. If so, replace the orifice. Call Stellar
Customer Service for instructions.
• Make sure the proportional valve is receiving 12V power when fully engaging the
transmitter trigger. If there is not 12V power while pulling the trigger, check for loose
connections inside the transmitter or replace the handle trigger assembly. If the
proportional valve is receiving 12 volts, loosen the solenoid holding nut and check to
see if the solenoid coil is magnetizing. If no polarity is present, replace the coil. If coil is
magnetizing, remove the stem valve, thoroughly clean, lubricate, and reinstall the valve.
Problem: Winch “Up”, Main Cylinder “Down”, and Extension Cylinder “Out” are the only
functions that don’t operate.
Solutions:
• Make sure that the anti-two block weight and chain on the end of the boom are straight so
they slide easily along the wire rope cable.
• Make sure that the limit switch is working properly. Disconnect the two wires connected to
the limit switch and tie them together. If all functions operate, replace the limit switch.
• Make sure that the cord for the cord reel is undamaged. Check the continuity of the cord.
Disconnect the cord reel from the crane harness and bypass the harness connection. If
the crane operates properly, replace cord reel.
Problem: Cylinder drifts outward or downward.
Solutions:
• Check to see if there is air in the hydraulic system. Operate all cylinders connected to the
hydraulic system. Start with the extension cylinder, then operate the main boom, winch,
rotation, and ending with the hydraulic stabilizers, if installed. When operating, extend
each cylinder halfway out, retract all the way in, and then extend until the cylinder rod
is at the end of its stroke. Operate cylinders slowly so air is pushed thru the system to the
reservoir. Repeat this cycle 2-3 times.
• Make sure the holding valves are operating properly. Note: Before performing any
maintenance on hydraulic components, relieve hydraulic oil pressure from all hydraulic
circuits. Remove, clean, and then inspect each holding valve. When removing a holding
valve, always relieve the pressure inside the cylinder by loosening jam nut of the holding
valve and turning set screw inward/clockwise. Count the number of turns until the set
screw is seated. When reinstalling the holding valve, make sure the valve is reset by turning
the set screw the number of turns it took to relieve the pressure. Finish by tightening the jam
nut.
• Check the cylinder rod for scratches. If a scratch is located on the cylinder rod, hydraulic
fluid can pass thru and cause a loss of pressure. Replace cylinder rod or cylinder.
• Check to see if the piston seals are damaged. If they show signs of damage, install a new
cylinder seal kit.
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