A high-volume rider electric pallet jack was experiencing bizarre, intermittent electrical faults. Sometimes it would drive forward perfectly. Other times, the operator would pull the handle back to drive forward, and the truck would violently drive in reverse, throwing the operator off the back step. The shop had already replaced the handle switch (the "wobble" paddle) twice, but the problem kept coming back.
Because the fault was intermittent, we knew it wasn't a straightforward short circuit. We put the truck on blocks and began physically manipulating the handle. We found that if we twisted the handle sharply to the left while pulling the switch, the truck would immediately drive backward. We took the handle assembly apart, but the wobble switch itself tested perfectly on a multimeter.
The problem wasn't the switch; it was the Printed Circuit Board (PCB) mounted inside the lower handle tube. To protect this board from moisture and vibration, the factory completely encases it in a hard, black epoxy-like substance called "potting compound." Over years of rough operation-operators violently slamming the handle against dock bumpers to turn-the physical stress transferred down the handle tube and caused microscopic, hairline cracks *inside* the rigid potting compound.
The copper traces on the PCB were intact, but the cracks in the epoxy allowed the traces to flex when the handle was twisted. When the handle was straight, the traces touched and the truck went forward. When the handle was twisted, the cracked epoxy shifted, pulling the copper traces apart, and the logic board defaulted to reverse. You couldn't see the crack, and you couldn't fix it without destroying the board to dig the epoxy out. We replaced the entire lower handle assembly, which solved the issue permanently. It's a frustrating reality of modern warehouse equipment: the electronics aren't failing because of electrical surges; they are failing because the physical casing around the electronics is cracking under the mechanical abuse of the operator.
