103
Ariston
Boiler Type Auto-Detection Failure
Thermostat shows error 103 and cannot detect any heating zones or boiler type during setup.
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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
Unsupported boiler protocol, Incorrect wiring to boiler terminals, Faulty boiler main PCB, Incorrect thermostat configuration profile
How to Fix / Troubleshooting
Safety: Switch off boiler and thermostat power before rewiring.
- Verify compatibility: Check the thermostat and boiler manuals to confirm that your Ariston smart thermostat supports the boiler model and protocol (OpenTherm, eBUS, on/off relay).
- Confirm correct terminals: Ensure the thermostat is connected to the correct boiler terminals (e.g. OT+/OT− for OpenTherm, TA/COM for on/off). Move wires if they are on wrong terminals.
- Manual configuration: Enter the thermostat’s installer menu and select the boiler type manually instead of auto-detect, following the Ariston installation guide.
- Reset to factory defaults: Perform a factory reset of the thermostat, then repeat the installation wizard carefully.
- If still failing: The boiler’s main PCB may not be responding on the bus; contact an Ariston service center to test the boiler electronics.
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Repair Difficulty
Hard
4/5
Required Part
Ariston Boiler Main PCB
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