Ariston gas water heater shows E04 and burner does not ignite or shuts down quickly.

Safety first: Turn off gas at the shutoff valve and disconnect electrical power. Work in a well-ventilated area. If you smell strong gas, evacuate and contact gas supplier/emergency services.

• Access burner and flame sensor: Remove the front cover. Locate the burner assembly and the ionization electrode (usually a small metal rod near the burner flame).
• Clean the flame sensor: Gently remove the sensor and clean the metal rod with fine emery cloth or a non-abrasive scouring pad to remove oxidation. Do not sand the ceramic insulator.
• Clean burner ports: Inspect burner for dust, rust, or debris blocking the ports. Use a soft brush and vacuum to clean. Do not enlarge the ports.
• Check electrode position: Reinstall the flame sensor ensuring the tip is correctly positioned in the flame path as per Ariston specifications (usually a few millimeters above the burner).
• Inspect wiring: Check the ignition/flame sensor cable for cracks or burns. Ensure firm connection to the control board.

Restore gas and power, then test. If E04 persists, the gas valve modulation or control board flame circuit may be faulty and should be diagnosed by a certified gas technician.