Furnace does not start; no inducer motor, no ignitor glow, no blower. LED flashes code 11 (no previous code stored).

Safety first: Turn off power to the furnace at the service switch and breaker before touching any wiring or components.

• Verify power supply: Confirm the furnace service switch is ON and the breaker is not tripped. Reset the breaker once if needed.
• Check door switch: Ensure the blower compartment door is fully closed and engaging the door safety switch on the control board bracket.
• Inspect thermostat wiring: Remove the furnace front panel, locate the low-voltage terminal strip on the control board (R, C, W, Y, G). Make sure the W (heat call) and R wires are firmly attached and not broken.
• Call for heat test: With power OFF, temporarily jumper R to W at the control board. Restore power and see if the furnace begins a heat cycle. If it does, the issue may be with the thermostat or thermostat cable.
• Clear code: Turn power OFF for 30 seconds, then ON. If code 11 returns but the furnace operates normally, it is only indicating no stored fault.

If the furnace still does not respond to a heat call and only shows code 11, the control board may not be processing the call and should be professionally tested.