A10
Beretta
Room Thermostat / Demand Signal Fault
Furnace shows A10, no heating demand recognized even when thermostat is calling for heat
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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
Open circuit in room thermostat wiring, Incorrect thermostat settings, Faulty Beretta control board input, Faulty room thermostat
How to Fix / Troubleshooting
Safety: Turn off power before working on low-voltage thermostat wiring.
- Check thermostat settings: Ensure the room thermostat is set to HEAT mode and the setpoint is above room temperature.
- Inspect wiring: At the furnace control board, locate the thermostat terminals (e.g., TA/TB or similar on Beretta boards). Verify wires are firmly connected and not corroded or broken.
- Bypass test (only if you are competent): With power off, temporarily link the thermostat input terminals at the control board using a short jumper wire. Restore power; if the furnace now recognizes demand and starts, the thermostat or its cable is likely faulty. Remove the jumper after testing.
If A10 persists with correct wiring and a known-good thermostat, the control board input may be defective and require replacement.
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Repair Difficulty
Medium
3/5
Required Part
Room Thermostat
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