I had a no power/no operation from a '94 Power Gear jack system occasionally and it turned out to be a corroded wire had broken off a hydraulic solenoid at the hydraulic manifold. The warning was that 'sometimes' it wouldn't operate and I'd mess around with stuff like the wiring, gear shift, plug/unplug connectors. But usually it would come back by itself...due to vibration it turned out. The second time it happened I recognised the symptoms immediately and found my solder job had failed. Did it up right that time...