Safety first: Turn off furnace power before handling thermostat wiring.

Step 1 – Verify thermostat settings: Ensure the thermostat is set to HEAT and the setpoint is above room temperature. Replace batteries if applicable.
Step 2 – Check low-voltage fuse: Remove the blower door and inspect the 3–5A fuse on the Ducane IFC. Replace if blown, but first inspect the thermostat wiring for shorts.
Step 3 – Test W call at furnace: With power off, remove the W wire from the board. Restore power and briefly jumper R to W at the board. If the furnace starts, the issue is in the thermostat or wiring.
Step 4 – Inspect thermostat cable: Look for damage along the cable run. Replace if crushed or cut.

Code 11; no response from the furnace when the thermostat calls for heat; LED indicates no previous faults.

Possible Causes