E19
Defro Flame Detection / Ionization Fault

Boiler shows E19, ignition occurs but flame is lost after a few seconds, repeated lockouts.

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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

Contaminated or misaligned Defro ionization electrode, Poor earth/ground connection on Defro boiler, Low gas pressure causing weak flame, Faulty flame detection circuit on Defro PCB

How to Fix / Troubleshooting

Safety: Isolate power and gas before accessing burner components.

  • Clean ionization electrode: Remove the ionization electrode from the burner. Gently clean the metal rod with fine emery cloth to remove oxidation and soot. Avoid damaging the ceramic insulator.
  • Check position: Ensure the electrode tip is correctly positioned in the main flame area as specified in the Defro service manual.
  • Verify grounding: Check that the burner and boiler chassis are securely bonded to earth. Tighten any loose earth screws.
  • Gas supply check: If other gas appliances show issues, contact your gas provider. Low pressure can cause weak flame and poor ionization.
  • Professional testing: If E19 persists, a technician should measure ionization current and inspect the PCB flame detection circuit.
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Repair Difficulty

Hard 4/5

Required Part

Defro ionization electrode
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