A cold storage facility reported that a Hangcha CPD30 electric forklift's hydraulic pump motor would start running as soon as the key was turned on, even without touching the steering wheel or lift lever. The battery was completely dead after 2 hours of sitting.
The technician first checked the "Pump Motor Contactor." The main contacts were welded (fused) together by an electrical arc. He pried them apart, but as soon as he reconnected the battery, the contactor snapped shut again. He checked the "Pilot Controller" output and found it was sending a continuous 24V signal to the contactor coil.
He traced the trigger wire to the "Power Steering Flow Amplifier" (a valve block on the steering axle). This valve uses a micro-switch (or pressure sensor) to detect when the steering wheel is turned, signaling the pump motor to provide oil. The micro-switch lever was stuck in the "Pressed" position. When he removed the valve cover, he found the "Flow Amplifier Spool" was jammed open by a piece of flash (excess plastic) from a previously replaced hydraulic hose. The jammed spool kept the micro-switch depressed, tricking the controller into thinking the operator was steering continuously, thus keeping the pump motor running.
The repair involved removing the debris from the flow amplifier spool, freeing the micro-switch lever, and polishing the spool with fine emery paper. The welded pump motor contactor was replaced. The hydraulic tank was inspected for debris. The forklift then only ran the pump motor when the steering was actuated or the lift lever was moved, restoring normal battery life.
