The Ropex RES‑409 (part 740903) is an impulse heat‑seal temperature controller that uses a microprocessor for sensorless, closed‑loop control of heating elements and stores set band alloy/temperature data in non‑volatile memory. Common failure points on this class include power‑supply dropout causing loss of stored settings, over‑current protection tripping on the heating element driver, and CAN bus communication errors that prevent proper band selection. First‑check diagnostics: verify 400 VAC input voltage and continuity to the controller’s main terminals; inspect the heat‑seal driver for signs of overheating or burnt components; review any logged error codes via the built‑in diagnostic display or connected CAN interface.[oss-gpt-20b]