118
Ariston
No Power to Thermostat
Error 118; thermostat cannot detect any power on its supply terminals.
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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
Tripped circuit breaker or fused spur, Loose live/neutral connections, Faulty 24 V transformer (if low-voltage model), Damaged power cable
How to Fix / Troubleshooting
Safety: Only work on mains circuits if you are qualified. Otherwise, call an electrician.
- Check breakers: Inspect the consumer unit and any fused spur feeding the thermostat/boiler. Reset tripped breakers and replace blown fuses with the correct rating.
- Verify boiler power: Ensure the boiler itself has power and is operating; some thermostats are powered from the boiler.
- Test voltage: Using a multimeter, measure voltage at the thermostat supply terminals (e.g. 230 V AC or 24 V AC as specified). If no voltage, trace back to the source and repair or replace the transformer or wiring.
- Secure connections: Tighten any loose terminal screws at the thermostat backplate.
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Repair Difficulty
Medium
3/5
Required Part
Ariston Thermostat Power Supply Transformer
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