Eurotronic
No Heat Output Despite Heat Demand
Room stays cold even though thermostat is calling for heat; boiler or valve does not activate.
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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 relay contacts in thermostat, Broken wiring between thermostat and boiler/actuator, Incorrect wiring to Eurotronic relay module, Boiler control input not compatible with thermostat output
How to Fix / Troubleshooting
Safety: This involves mains voltage. Turn off power at the breaker and verify with a tester before working on wiring.
- Check display: Confirm that the thermostat actually shows a heat demand (flame icon or similar). If not, check setpoint and schedule.
- Inspect wiring: Remove the thermostat cover and verify that the control wires are connected to the correct terminals (e.g., COM and NO for on/off control) and that screws are tight.
- Bypass test (advanced): At the boiler or relay module, briefly bridge the control terminals that the thermostat normally switches. If the boiler starts, the issue is in the thermostat or its wiring.
- Check compatibility: Ensure the Eurotronic thermostat output type (voltage-free contact, 24V, or 230V) matches the boiler input requirements.
- Replace thermostat/relay: If wiring and compatibility are correct but no output is present when calling for heat, replace the thermostat or external relay module.
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Repair Difficulty
Hard
4/5
Required Part
Output Relay / External Relay Module
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