A heavy-duty, LP-gas powered forklift was brought in with an intermittent, complete electrical shutdown. The operator could drive the truck straight all day long, but the moment they turned the steering wheel to the right while pulling a heavy load up a ramp, the entire truck would instantly die-no spark, no dash lights, nothing. If they let go of the steering wheel, the power would mysteriously return.
The shop assumed there was a chafed wire in the steering column shorting out when turned. They spent hours tearing apart the dash and the wiring harness, finding nothing. We looked at the electrical schematics and the physics of the machine. This truck had an electronic throttle and an engine ECM that operated on 12 volts. The power steering was a massive, gear-driven hydraulic pump.
When the operator cranked the steering wheel hard into a load on an incline, the power steering pump hit maximum pressure relief, demanding a huge surge of mechanical torque from the engine. This sudden load caused the engine RPM to dip for a fraction of a second. At that exact moment, the alternator's output dropped. The ECM relies on a steady 12-volt supply; if the voltage drops below 9 volts, the computer instantly shuts off to protect its memory.
We tested the battery cables. The positive terminal clamp had a microscopic layer of green corrosion inside the crimp, creating high resistance. Under normal running, the alternator pushed 13.5 volts through it fine. But when the steering load caused the alternator output to dip, the resistance in the corroded clamp caused a massive voltage drop, starving the ECM of power and killing the engine. We cut off the old clamp, crimped on a new heavy-duty terminal, and the truck never died in a turn again. When an engine dies under sudden heavy load, always suspect the battery cables before the complex electronics.
