117
Ariston
Stuck Heating Relay / Output Failure
Thermostat shows error 117 and reports that the relay output is stuck or not responding.
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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
Welded relay contacts due to overload, Faulty solid-state relay on PCB, Incorrect wiring causing short circuit, Excessive load on thermostat output
How to Fix / Troubleshooting
Safety: Isolate power to the thermostat and boiler before any wiring or relay checks.
- Check load rating: Confirm that the connected boiler or zone valve load does not exceed the thermostat’s maximum switching current. If it does, an external relay or contactor must be used.
- Test operation: With power restored, command heating on and off while listening for relay clicks. If the boiler stays on regardless of command, the relay is likely welded.
- Inspect wiring: Ensure that live and switched live are correctly wired to COM and NO terminals as per the Ariston diagram, and that there are no shorts.
- Replace thermostat or add external relay: A stuck internal relay requires thermostat replacement. For high loads, install an external relay module controlled by the thermostat.
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Repair Difficulty
Hard
4/5
Required Part
Ariston Thermostat Relay Output
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