Boiler will not start at all; no lights or display, completely dead

Safety first: Before working on electrical components, turn off the breaker and verify power is off with a non‑contact tester.

• Check breaker and switch: Verify the boiler circuit breaker is ON and the boiler service switch (often near the unit) is in the ON position.
• Inspect power connections: Remove the electrical junction box cover on the boiler. Confirm wire nuts are tight and no wires are burned or disconnected.
• Look for internal fuse: Some Ruud boilers have an internal line fuse on the control board. If accessible, inspect and replace only with the exact same type and rating.
• If still dead: The main control board or transformer may have failed. Further live‑voltage testing should be done by a licensed technician.