Water heater does not start, burner will not ignite, lockout symbol on display

Safety first: If you smell gas, do not attempt repair. Ventilate the room, close the gas shut‑off valve, and contact your gas supplier or a qualified technician immediately.

Step-by-step checks:

• Reset the heater: Turn the main power switch off for 30 seconds, then back on. Press the reset button (if present) on the De Dietrich control panel and observe if E01 reappears.
• Check gas supply: Ensure the external gas shut‑off valve is fully open. Verify that other gas appliances in the home work. If not, the issue may be with the building gas supply.
• Inspect combustion air and flue: Make sure the air intake and flue outlet are not blocked by debris, snow, or nests. A blocked flue can prevent ignition.
• Inspect ignition electrode: With power and gas OFF, remove the burner access panel. Locate the ignition electrode on the burner assembly. Check for cracks in the ceramic, heavy soot, or corrosion. Clean the tip gently with fine emery cloth and re‑seat the electrode firmly.
• Check wiring to ignition and flame sensor: Verify that the ignition cable and flame ionization cable are firmly connected to the control board and electrodes. Look for burn marks or damaged insulation.
• Gas valve check (visual only): Confirm the wiring harness is fully seated on the De Dietrich gas valve. Do not attempt to open or adjust the gas valve yourself; this must be done by a certified gas technician.

When to call a professional: If E01 persists after reset and basic checks, or if the ignition electrode or gas valve needs replacement, contact an authorized De Dietrich service center. Gas adjustments and combustion analysis require specialized tools.