Boiler shows A17; ionization signal present without flame, immediate lockout.

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

Shorted ionization electrode to burner, moisture on electrode, faulty control board flame circuit, incorrect grounding of boiler.

Safety: Isolate power and gas. Wait for components to cool.

1. Inspect ionization electrode: Remove the electrode and check for carbon tracking, cracks, or moisture. Clean and dry thoroughly or replace if damaged.
2. Check wiring: Ensure the ionization cable is not touching grounded metal parts and that insulation is intact.
3. Verify earth connection: Confirm that the boiler has a solid protective earth connection. Poor grounding can cause false flame signals.
4. Control board: If the electrode and wiring are good, the flame detection circuit on the PCB may be defective and require replacement.

Hard 4/5

Ionization Electrode

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