E12
Defro
Flame Instability / Poor Combustion
Boiler displays E12, burner shuts down shortly after ignition, sometimes with noisy combustion.
Advertisements
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.
Advertisements
Possible Causes
Incorrect gas/air ratio on Defro burner, Blocked or partially blocked burner injectors, Flue restriction causing poor draft, Faulty gas valve modulation control on Defro PCB
How to Fix / Troubleshooting
Safety: Combustion adjustments must be performed by a qualified gas technician with a flue gas analyzer.
- Visual inspection: With power off, remove the burner assembly from the Defro combustion chamber if accessible. Check for heavy soot, rust, or debris on the burner surface and injectors.
- Clean burner: Use a soft brush and vacuum to clean the burner head and surrounding area. Do not enlarge injector holes.
- Check flue and air intake: Ensure the Defro flue terminal and air intake are clear of obstructions as described for E03.
- Professional tuning: If E12 persists, a technician must check gas inlet pressure, adjust the gas valve, and verify CO/CO2 levels to manufacturer specifications.
Advertisements
Repair Difficulty
Professional Required
5/5
Required Part
Defro burner assembly
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements