Lochinvar condensing gas water heater will not ignite; display shows E001 and burner never lights.

Safety first: Turn off power to the water heater at the breaker and shut off the gas supply valve before touching any wiring or gas components. If you ever smell gas, stop immediately and contact your gas utility or a licensed technician.

Step-by-step checks:

• 1. Verify gas supply: Ensure the manual gas shutoff valve to the Lochinvar heater is fully open. Confirm other gas appliances in the home are working. If not, there may be a supply issue.
• 2. Reset the unit: Restore power, then follow the user manual to clear the E001 lockout (usually by pressing and holding the reset button or cycling power). Observe if the unit attempts ignition.
• 3. Inspect the igniter: With power off, remove the burner access panel. Locate the hot surface igniter or spark igniter assembly. Check for cracks, heavy white deposits, or broken wiring. A damaged igniter should be replaced as a complete Lochinvar igniter assembly.
• 4. Check flame sensor: The flame sensor rod should be clean and positioned in the burner flame path. Lightly clean it with fine steel wool or emery cloth to remove oxidation, then reinstall.
• 5. Inspect wiring and connectors: Verify all harness plugs between the ignition control board, gas valve, igniter, and flame sensor are fully seated and not corroded or heat-damaged.
• 6. If still no ignition: If the igniter tests open with a multimeter or the control never sends power to the igniter, the ignition control board or gas valve may be defective. At this point, contact a qualified Lochinvar service technician for gas pressure testing and control board diagnostics.