Ariston DHW Flow Sensor / Turbine Fault

Boiler displays error code 702: hot water demand is not recognized, and there is no burner ignition when a hot tap is opened.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Stuck or blocked DHW flow turbine, Faulty flow sensor, Blocked inlet filter, Wiring fault between sensor and PCB

Safety: Turn off power and isolate the cold water supply to the boiler before removing any water components.

Check tap flow: Ensure there is adequate water flow at hot taps. Very low flow may not trigger the sensor.
Clean inlet filter: Many Ariston boilers have a cold water inlet filter. Remove and clean it of debris and limescale.
Inspect DHW flow sensor: The DHW flow turbine/sensor is usually on the cold inlet. It can become jammed with debris. Carefully remove and clean or replace it, ensuring the O-rings are in good condition.
Reset and test: Restore water and power, then open a hot tap to test. If error 702 persists, the sensor or PCB may need replacement by an engineer.

Medium 3/5

DHW Flow Sensor / Turbine

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