The Danfoss 1940 Controller is an industrial electronic temperature/drive control unit used in HVAC and motor drive applications. Common failure modes include power supply voltage drops, burnt-out I/O relays, firmware corruption, and overheating of the main board due to inadequate ventilation or dust accumulation. Begin troubleshooting by verifying input voltage and grounding integrity, inspecting the board for visible damage (burn marks, cracked components), and checking all user‑accessible I/O terminals for continuity and correct wiring per the wiring diagram. If available, review any stored error codes via the controller’s diagnostic port before proceeding with component replacement.[oss-gpt-20b]