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

Safety: You will be working near 120/240 V. If unsure, call an electrician.

Steps:

• Check the main electrical panel and reset any tripped breaker feeding the furnace.
• Verify that the furnace service switch (often looks like a light switch near the unit) is ON.
• Remove the blower door and check the door safety switch; ensure the door is properly installed to depress the switch.
• Inspect the control board for a small automotive-style fuse; if blown, replace with the same amperage. If it blows again, there is a short in the low-voltage circuit that needs diagnosis.
• Check wire connections in the furnace junction box for loose wirenuts or burned wires.