Ariston Air Pressure Switch / Differential Pressure Fault

Boiler displays 602, intermittent fan-related lockouts, sometimes works after reset

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

Blocked pressure tubes, Faulty air pressure switch, Partially blocked flue, Weak fan not generating sufficient pressure

Safety: Do not tamper with sealed combustion components unless qualified.

Check flue terminal: Ensure no debris or vegetation is blocking the terminal.
Engineer tasks: An engineer will inspect and clean the air pressure switch tubes, test the switch operation, and verify fan performance.
Do not bypass: Never bridge the air pressure switch to force operation; this is extremely dangerous.

Professional Required 5/5

Air Pressure Switch

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