Status LED solid on with no flashing, furnace not responding to thermostat

Safety first: Turn off power before touching low-voltage wiring to avoid shorting the transformer.

Steps to check:

• Verify thermostat settings: Ensure the thermostat is set to HEAT and the setpoint is above room temperature. Replace thermostat batteries if applicable.
• Check low-voltage fuse: Remove the blower door and locate the 3–5A automotive-style fuse on the control board. If blown, replace with the same rating. If it blows again, there is a short in the low-voltage circuit that needs professional diagnosis.
• Inspect thermostat wiring: Confirm the W (heat) wire is securely connected at both the thermostat and furnace control board.
• Reset control: Turn furnace power off for 30 seconds, then back on. Watch for any new flash codes.