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.

All Skyjack mobile elevating work platforms are equipped with a manual storage box. The weather resistant plastic box is located either on the platform or in the base control area. The manual storage box should always be in good condition – attached securely to the machine, no missing parts, and weather tight to keep the documents inside clean and dry. The box contains important documents for personnel who use the mobile elevating work platform - the ANSI Manual of Responsibilities and the Skyjack Operating Manual for that model and serial number.