Ariston gas water heater displays E07 and will not run; often associated with fan-type models.

Safety first: Isolate gas and electrical power. Do not bypass safety devices.

• Access fan assembly: Remove the front cover. Locate the combustion fan and air pressure switch (small round device with tubing).
• Check fan rotation: With power briefly restored, observe if the fan attempts to start (do not leave covers off during extended operation). If it hums but does not spin, the motor may be seized.
• Inspect for obstructions: With power off, spin the fan wheel by hand. Remove any debris and ensure it rotates freely.
• Inspect pressure tubing: Check silicone tubes from the fan housing to the pressure switch for splits, kinks, or disconnections. Refit or replace as needed.
• Test pressure switch: Using a multimeter, verify continuity change on the switch when gently applying suction/pressure to the tube (only if you are trained to do so).

If the fan or pressure switch is defective, replacement is recommended to be carried out by a certified gas technician due to combustion safety implications.