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

Safety: Do not work inside the furnace with power on. Use a non-contact voltage tester if available.

Steps to check:

• Check breaker: Locate the furnace circuit breaker in the electrical panel. If tripped, reset once. If it trips again, call a technician.
• Verify furnace switch: Ensure the furnace service switch (often looks like a light switch near the unit) is in the ON position.
• Door switch: Confirm the blower door is fully closed and engaging the door safety switch. Many Ruud furnaces will not power the board with the door off.
• Inspect board fuse: With power off, remove the blower door and locate the low-voltage automotive-style fuse (3–5A) 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.