Water heater will not fire, display shows F1 shortly after a call for hot water or heating.

Safety first: Turn off electrical power to the water heater at the isolator and close the gas isolation valve before removing any covers. Allow the unit to cool fully.

• Check gas supply: Confirm the external gas isolation valve is open and that other gas appliances in the property work. If there is a gas supply issue, contact your gas supplier.
• Inspect burner viewing window: Through the inspection window (if fitted), check for signs of heavy soot or debris on the burner. Do not attempt to scrape the burner with sharp tools.
• Clean flame sensor: Remove the front cover following the Ideal service manual. Locate the flame sensor (flame rectification electrode) near the burner. Gently clean the metal rod with a fine abrasive pad or emery cloth to remove oxidation. Do not bend the rod.
• Check wiring: Ensure the flame sensor lead is firmly connected to the control board and not damaged or burnt.
• Reset the heater: Restore power and gas, then reset the unit using the front panel reset procedure. If F1 returns repeatedly, stop using the heater and contact a qualified technician.