Furnace does not start at all; no display, no fan, completely dead.

Safety: Turn off the circuit breaker before opening the electrical compartment.

Steps:

• Check breaker and switch: Verify the furnace breaker is ON and that any local disconnect switch is in the ON position.
• Inspect power wiring: Confirm that live, neutral, and earth wires are securely connected at the furnace terminal block.
• Check internal fuse: Replace any blown fuse on the control board with the exact same rating.

Professional service: If the furnace remains dead, the control board or internal transformer may be faulty and should be replaced by a technician.