A2
Miller
Pressure Switch Fault (Advanced Board)
Miller furnace digital display shows A2; inducer runs but burners do not light.
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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
Blocked vent or intake, Failed inducer motor not achieving draft, Faulty pressure switch, Water in pressure tubing
How to Fix / Troubleshooting
Safety: Shut off power before disconnecting tubing or wiring. Do not operate the furnace with venting removed.
- Check vent terminations: Inspect outside terminations for obstructions such as snow, ice, or debris. Clear as needed.
- Inspect condensate system: On condensing Miller furnaces, check the condensate trap and hoses for clogs. Clean and flush the trap, ensuring proper slope.
- Drain and clear tubing: Remove pressure switch tubing and blow through it to clear water or debris. Reconnect firmly.
- Test pressure switch: Use a manometer or continuity tester to verify the switch closes when the inducer is running. Replace the switch if it fails to close at the specified pressure.
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Repair Difficulty
Hard
4/5
Required Part
Pressure Switch
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