Furnace will not start at all; no inducer, no blower, no LED lights on the control board.

Safety first: Be cautious when working around 120V circuits. Turn off the breaker before removing electrical covers.

• Check breaker and switch: Locate the furnace breaker in the electrical panel and reset if tripped. Verify the furnace service switch (often looks like a light switch near the unit) is ON.
• Verify door switch: Ensure the blower door is properly installed and depressing the door safety switch. The furnace will not power up with the door removed.
• Inspect internal wiring: With power off, remove the blower door and check that the line voltage wires are securely connected to the control board or junction box.
• Check transformer (basic): If the board has no 24V output and the transformer looks burned or smells burnt, it may need replacement.

If you are not comfortable working with line voltage, contact a professional electrician or HVAC technician.