Boiler locks out with F.01 on display, no ignition, status light red

Safety first: Turn off electrical power to the boiler at the service switch and close the gas shutoff valve before removing any covers. Allow the boiler to cool completely.

• Check gas supply: Verify the manual gas shutoff valve to the boiler is fully open. Confirm other gas appliances in the building operate normally. If gas supply is questionable, contact your gas utility or a licensed gas fitter.
• Inspect flame sensor (flame rod): Remove the burner access panel. Locate the flame sensor on the burner assembly. Disconnect the wire and remove the sensor. Clean the metal rod gently with fine emery cloth or a Scotch-Brite pad to remove oxidation. Do not sand the ceramic insulator. Reinstall and ensure the wire connection is tight.
• Inspect ignition electrode and cable: Check for cracked ceramic, carbon tracking, or loose connections. Ensure the electrode gap and position match the Lochinvar service manual for your model. Replace the ignition electrode assembly if damaged.
• Check burner and combustion area: Inspect the burner for debris, rust flakes, or blockage. Vacuum loose debris with a soft brush attachment. Do not alter burner ports.
• Reset and test: Restore power and gas, then reset the boiler using the control panel. Observe ignition sequence through the sight glass. If F.01 returns, further testing of gas valve operation and flame signal microamps should be performed by a qualified technician.

When to call a professional: If you suspect low gas pressure, faulty gas valve, or if the boiler repeatedly fails to ignite after cleaning the flame sensor, contact a licensed heating technician. Do not attempt to adjust gas valve settings yourself.