Thermostat displays a warning that the furnace is not responding when a heat call is made

Safety: Turn off power to the furnace/air handler at the breaker before working on wiring.

• Step 1 – Verify ecobee configuration: Go to Menu > Settings > Installation Settings > Equipment and confirm that a heat stage is assigned to the W1 terminal.
• Step 2 – Inspect W wire at thermostat: Remove the ecobee and ensure the W1 wire is fully inserted and clamped. Tug gently to confirm it is secure.
• Step 3 – Inspect W wire at furnace: Open the furnace panel and verify the same W wire is connected to the W terminal on the control board. Tighten the screw.
• Step 4 – Check furnace fuse: Locate and inspect the 3A low-voltage fuse on the control board. Replace if blown, but investigate for shorts if it blows again.
• Step 5 – Test W circuit: With power on, temporarily jumper R to W at the furnace control board. If the furnace starts, the board is good and the issue is between the board and thermostat. If it does not start, the board or furnace safety chain may be faulty and a technician should be called.