A1
Miller
Ignition Lockout (Advanced Board)
Miller furnace with advanced digital display shows code A1 and fails to ignite.
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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
Failed hot surface ignitor, No gas flow to burners, Faulty flame sensor, Defective ignition module
How to Fix / Troubleshooting
Safety: Turn off gas and power before servicing. Ignition lockouts often follow repeated failed ignition attempts.
- Reset control: Turn power off for 30–60 seconds, then back on. Attempt a heat call and observe the sequence.
- Inspect ignitor: Remove and visually inspect the Miller hot surface ignitor for cracks or damage. Test resistance with a meter; an open circuit indicates failure. Replace if defective.
- Verify gas supply: Confirm the manual gas valve is open and other gas appliances operate. Listen for the gas valve click during ignition. If no gas flow with 24V present, replace the gas valve.
- Clean flame sensor: Remove and clean the flame sensor rod with fine abrasive pad. Reinstall securely.
- Replace ignition module/control board: If all components test good but A1 persists, the integrated ignition module may be faulty and require replacement with the correct Miller board.
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Repair Difficulty
Hard
4/5
Required Part
Hot Surface Ignitor
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