E1 displayed, furnace does not respond to thermostat call for heat

Safety first: Turn off furnace power at the breaker and service switch before removing any panels.

• Step 1 – Inspect thermostat wiring at furnace: Remove blower door, locate R and W terminals on the Ducane IFC. Ensure wires are firmly attached and not broken or corroded.
• Step 2 – Bypass thermostat (test only): With power OFF, temporarily connect a jumper between R and W at the control board. Restore power. If the furnace starts a heat cycle without E1, the thermostat or thermostat cable is likely faulty.
• Step 3 – Check for shorts: Inspect thermostat cable along its run, especially where it passes through walls or sheet metal. Look for crushed, cut, or bare conductors touching metal.
• Step 4 – Test thermostat: Remove thermostat from its base and check that it is correctly configured for a gas furnace (not heat pump) and that the R and W terminals are tight. Replace thermostat if suspected faulty.
• Step 5 – Remove jumper: After testing, turn power off and remove the R-W jumper. Do not leave the jumper installed for normal operation.