Water heater will not fire; control display or LED indicates 'Hard Lockout' and burner remains off until power is cycled or reset button is pressed.

Safety first: Turn off power to the water heater at the service switch or breaker and shut off the gas valve before removing any covers. Allow the unit to cool.

• Check for obvious lockout cause: Many Weil-McLain controls will show a history or reason for lockout (e.g., ignition failure, flame failure). Note any messages or LED blink patterns before resetting.
• Reset the control: Restore power and follow the manufacturer’s reset procedure (often pressing and holding the reset button for several seconds). If the unit immediately returns to Hard Lockout, do not continue to reset repeatedly.
• Inspect high limit and rollout switches: With power off, locate the high limit and flame rollout switches on the burner compartment. Check for manual reset buttons; press firmly to reset if tripped. If a switch immediately trips again, there is a combustion or venting problem that must be corrected.
• Check gas supply: Verify the manual gas shutoff valve is fully open and that other gas appliances are operating normally. Low or no gas pressure can cause repeated ignition failures.
• Inspect flame sensor and igniter: Remove and visually inspect the flame sensor rod and hot surface igniter or spark electrode. Clean light surface oxidation with fine emery cloth and reinstall, ensuring proper positioning in the flame path.
• When to call a professional: If the Hard Lockout recurs after a single reset, or if you see signs of overheating, soot, or melted wiring, stop troubleshooting and contact a qualified Weil-McLain technician. Persistent lockouts can indicate unsafe combustion or a failing control module.