The 4-way valves used on skyjack equipment use a simple coil operated sliding spool design to direct oil to the correct function. (See figure 1) When one of the coils is energized, the spool shifts position opening one port to the function and the opposite port to the return to tank. The flow of oil to the correct port only occurs when the spool slides to either side. In some instances of a function failure, the valve coil may have power and ground signals at the correct electrical coil terminals but no function operation. In order to test that the spool is not stuck, we can use the manual override built into the valve.
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The Skyjack full-size rough terrain scissor lift models 8831/8841 and 9250 offer single or dual hydraulic extension decks as an option. These optional hydraulically powered decks extend and retract using a cylinder and hydraulic power pack mounted under the platform and operated from a small control box located on the main platform. When the key/selector switch on the main control box is positioned in the LIFT mode, the power extend deck circuit is enabled, allowing power extension deck operation.
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The joystick controllers used on the Skyjack SJIII Compact and Conventional scissor lifts, the SJ12/16 Mast lifts, and the Rough Terrain scissor lifts have incorporated a change to the enable circuit of the joystick. You may notice this change when you are troubleshooting the machine. Once the enable trigger is squeezed, an internal timer starts running; if a function is not operated within 7 seconds, the enable circuit is shut off and the joystick trigger must be released and depressed again to reset the enable circuit. The 7 second cut-out is used to inhibit tampering with or bypassing the enable switch with tape, a zip tie, or other means.
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The new style hydraulic pumps used on the Skyjack Compact and Conventional model electric scissor lifts mount to the pump motor with two socket head cap screws. You will see four cap screws at the front face of the pump. Two of the cap screws hold the pump body together, and the other two cap screws secure the pump to the motor face plate. To remove the pump, you need only to remove the mounting cap screws that are missing from figure 1....
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The tilt switches used on Skyjack aerial work platforms are safety devices that sense when the machine is out of level in any direction. The tilt switch is a normally closed switch that opens once it is tilted beyond a preset angle. Once the tilt switch opens, the tilt switch circuit will then sound an alarm and/or cut-out functions. The tilt switches are programmed for angle ranges that are specific to each aerial lift model. For this reason, when replacing a tilt switch,
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The Skyjack Compact Rough Terrain scissor models 6826/6832 R/T may be equipped with outriggers to level the frame when used on uneven terrain. The outrigger assemblies attach to the machine frame via weldments that bolt to the frame rails at the front and the rear. The outrigger cylinder assemblies slide into the weldment and are bolted in place from underneath. It is important to inspect the outrigger weldments and cylinder assemblies regularly for missing parts, damage, or loose components or fasteners.
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