Boiler will not ignite; display shows A01 lockout, fan may run briefly then stop, no flame established.

Safety first: Turn OFF power to the boiler at the service switch and shut OFF the gas supply before removing any panels. Allow the unit to cool completely. If you smell gas continuously, evacuate the area and contact your gas supplier or a licensed technician immediately.

Step-by-step checks:

• 1. Verify gas supply: Confirm the manual gas shutoff valve to the Raypak boiler is fully open. Check that other gas appliances in the building are operating normally. If gas supply is questionable, contact your gas utility.
• 2. Inspect the igniter/flame sensor assembly: Remove the burner access panel. Locate the hot surface igniter or spark igniter/flame sensor assembly. Look for cracks, heavy white buildup, or soot. Clean the flame sensor rod gently with fine emery cloth or a Scotch-Brite pad until shiny. Do not touch the igniter element with bare fingers.
• 3. Check wiring connections: Inspect the harness from the ignition control module to the igniter and flame sensor. Ensure all connectors are fully seated and not corroded or damaged. Repair or replace any burnt or brittle wiring.
• 4. Confirm proper grounding: Raypak ignition systems require a solid ground for flame rectification. Verify the ground wire from the control board to the chassis is tight and free of rust. Clean contact surfaces if needed.
• 5. Reset and test: Restore power and gas. Follow the Raypak manual to clear the A01 lockout (usually by cycling power or pressing the reset button on the control). Observe ignition. If the boiler still fails to light, the igniter or ignition control module may need replacement.

When to stop: If you are not comfortable working around gas and high voltage ignition components, or if A01 returns repeatedly after cleaning and checking connections, contact a qualified Raypak service technician.