The Valley Electromagnetics 71‑400‑24AD Motor Controller is a high‑current industrial drive used to regulate DC motor speed and torque in process equipment. Common failure modes for this class of controllers include power supply overheating, capacitor degradation on the input filtering stage, and over‑temperature shutdown due to inadequate ventilation or fan failure; these can manifest as intermittent operation, no output, or audible whining from a failing fan. First‑check diagnostics: verify that the 24 V DC input is within spec and stable, inspect all capacitors and fuses for bulging or burn marks, and confirm that the cooling fan is spinning and free of obstruction; review any error codes displayed on the controller’s diagnostic LED panel before proceeding to deeper module testing.[oss-gpt-20b]