A21
Ferroli
Fan Speed Control / Tachometer Fault
Ferroli furnace shows A21; may be associated with incorrect fan speed or noisy operation.
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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
Faulty fan speed sensor (tachometer) on Ferroli fan, Loose fan connector, Control board fan driver fault
How to Fix / Troubleshooting
Safety: Isolate power before accessing the fan or control board.
Steps:
- Visual inspection: Remove the front cover and locate the fan connector on the fan housing and control board. Ensure all plugs are fully seated.
- Check for obstructions: Look for foreign objects or insulation touching the fan wheel that could slow it down.
- Reset: Restore power and reset the unit. If A21 persists, the fan or control board is likely defective.
Professional help: Fan replacement and control board diagnostics should be performed by a technician.
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Repair Difficulty
Hard
4/5
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