Intermittent electrical issues are the absolute worst, and a local distribution center had a three-wheel electric reach truck that was driving their maintenance team crazy. Once or twice a shift, the power steering would completely lock up. The operator would turn the key off, turn it back on, and it would work fine for another four hours. There were no fault codes on the dash.
Because it was an electric power steering (EPS) system, we knew the issue was either the motor, the controller, or a sensor. We ruled out the steering motor because when it worked, it had full torque with no grinding or noises. We put a laptop on the CAN bus system and left it hooked up to the truck while a driver ran it for a full day.
It took six hours, but we finally caught the glitch. The CAN bus log showed a micro-second voltage drop to the steering angle sensor right before the failure. We traced the wiring harness from the steering column down to the chassis. Where the harness passed through a rubber grommet on the floor plate, the insulation had rubbed through on the sharp metal edge. The bare wire wasn't quite touching the frame, but the heavy vibration of the reach truck moving over dock plates was causing the wire to intermittently arc against the chassis. This momentary short was confusing the EPS controller, which immediately shut down the steering as a safety precaution to prevent uncontrolled movement. We soldered the wire, wrapped it in heavy-duty split loom, and re-routed it with a zip-tie away from that edge. It took six hours of monitoring to find a problem that required five minutes to fix, but that's the reality of modern electric forklift diagnostics-you can't just look for broken parts anymore; you have to chase electrons.
