The status LED flashes green rapidly; the furnace blower runs but the burners do not ignite.

Safety first: Turn off power before moving thermostat wires.

Steps to check:

• Verify thermostat fan setting: Set the fan mode to AUTO instead of ON. Ensure the system mode is set to HEAT when testing furnace operation.
• Check thermostat wiring: Confirm that the G (fan) wire is connected only to G at both the thermostat and furnace. Ensure there is no jumper between G and W that would cause unintended fan operation.
• Test G circuit: Remove the G wire from the furnace control board. If the blower stops and the LED returns to normal, the thermostat or wiring is energizing G continuously.
• Board relay check: If the blower runs even with the G wire removed, the fan relay on the control board may be stuck closed, and the board will need replacement.

Correct thermostat wiring issues or replace the thermostat if it is sending incorrect signals. Replace the control board if the fan relay is stuck.