Boiler shows E1 338, may indicate unstable flame or ionisation signal.

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

Partially blocked burner, Incorrect gas pressure, Faulty ionisation electrode, Flue gas recirculation

Safety first: Combustion-related work must be done by a Gas Safe engineer.

Engineer actions:

Inspect and clean the burner and primary heat exchanger surfaces.
Check and clean the ionisation electrode; ensure correct position in the flame.
Measure gas inlet and burner pressures and adjust or replace the gas valve as required.
Inspect the flue system for recirculation issues and correct any installation faults.

Professional Required 5/5

Ionisation Electrode

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