A12
Beretta
Flame Signal Too Weak / Ionization Fault
Furnace shows A12, burner shuts down and may restart after a delay
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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
Dirty ionization probe, Poor grounding of furnace, Incorrect burner flame pattern, Faulty ionization circuit on control board
How to Fix / Troubleshooting
Safety: Turn off power and gas before servicing the flame detection system.
- Clean ionization probe: Remove the ionization probe from the burner. Clean the metal rod with a fine abrasive pad until shiny. Avoid damaging the ceramic insulator.
- Check grounding: Verify the green/yellow ground wire from the mains supply is firmly attached to the furnace chassis and the control board ground terminal. Tighten any loose screws.
- Inspect burner flame: After reassembly, observe the flame through the sight glass. It should be stable and mostly blue. Yellow tips or lifting flames indicate combustion issues that require professional adjustment.
If A12 persists, the control board's ionization circuit may be defective and should be replaced by a qualified technician.
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Repair Difficulty
Hard
4/5
Required Part
Ionization Probe
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