203
Ariston Fan / Air Pressure Switch Fault

Boiler shows 203, fan runs but no ignition, or stops unexpectedly

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Safety Warning

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.

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Possible Causes

Faulty fan motor, Blocked flue or air intake, Defective air pressure switch, Split or blocked pressure tubing

How to Fix / Troubleshooting

Safety: Flue and combustion air issues are safety critical. Do not operate the boiler if you suspect a flue blockage.

  • External flue check: Inspect the flue terminal for obstructions. Do not alter the flue assembly.
  • Listen to fan: When there is demand, the flue fan should start and run smoothly. Grinding or no operation indicates failure.
  • Pressure tubes: An engineer can inspect the silicone tubes from the fan/venturi to the air pressure switch for blockages or splits and replace if needed.
  • Switch test: The air pressure switch contacts should close when the fan runs. This test and any replacement should be done by a professional.
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Repair Difficulty

Professional Required 5/5

Required Part

Fan Assembly
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