Furnace completely dead; no LED lights, no blower, no inducer operation.

Safety: Use caution when working around live electrical circuits. Turn off the breaker before opening electrical compartments.

Steps to check:

• Check breaker: Locate the furnace breaker in the electrical panel. If tripped, reset once. If it trips again, do not continue resetting.
• Verify service switch: Ensure the furnace service switch (often mounted on or near the furnace) is in the ON position.
• Inspect board fuse: Remove the blower door and locate the low-voltage fuse (often 3–5 amp automotive-style) on the control board. Replace only with the same type and rating if blown.
• Check door switch: Confirm the blower door is installed correctly to engage the door switch.

When to call a technician: If the fuse blows repeatedly, or if there is still no power after these checks, a professional should test the transformer and wiring.