The Monsun‑Tison RT505A is a control and drive module used in Caterpillar reach forklifts, integrating high‑power motor drives, PLC logic, and safety interlocks for lift and reach operations. Common failure points on this class of units include degraded power supply rails (±48 VDC), overheating of the main MOSFET array or IGBT modules, failed gate driver ICs, and corrupted firmware or lost communication with the forklift’s central controller. Initial checks should verify that the unit receives correct input voltage and current from the forklift battery, inspect the heat sink and cooling fan for dust buildup or mechanical failure, and review any diagnostic error codes logged in the onboard PLC or external diagnostics port.[oss-gpt-20b]