A manufacturing warehouse reported that a Clark CGEN2 30 electric forklift jerked violently (cogged) when accelerating in forward or reverse. When the operator attempted to lift a heavy load, the hydraulic pump would start, immediately stop, and the dashboard would display a "Low Voltage" fault.
The technician connected a digital multimeter directly across the traction motor controller terminals. With the key on but no functions operated, the battery voltage was 48.2V. When the operator pressed the accelerator, the voltage plummeted to 28V, and the motor cogged. This extreme voltage drop under load indicated massive resistance in the main power circuit.
He inspected the main battery connector (an SB-style plug). There was a distinct smell of burnt plastic, and the plastic housing around the positive pin was melted. The connector pins were blackened and corroded. The high resistance at the melted connector caused the voltage to drop before it ever reached the controller.
To ensure the rest of the circuit was healthy, he bypassed the connector with a heavy-duty jumper cable. The drive function became smooth, but the lift still cut out. He then opened the main "Line Contactor" housing. The main contact tips were severely pitted and burnt from years of arcing during high-current disconnects. The pitted tips added further resistance, causing the voltage to drop below the controller's 32V minimum threshold when the hydraulic pump motor engaged, triggering the protective cutout.
The repair involved replacing the melted battery connector housing and installing new silver-plated contact pins. The main line contactor was replaced as a complete assembly. The battery cells were individually load-tested to ensure no internal cell degradation had occurred from the repeated high-resistance heating. After reassembly, the forklift accelerated smoothly, and the hydraulic lift operated continuously without voltage drop faults.
