Worcester
Short Cycling Due to Control or Sensor Issues
Boiler starts then shuts down after a few seconds, radiators barely warm, no error code displayed.
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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 room thermostat or wiring, NTC sensor misreading temperature, oversized boiler with no modulation control, blocked bypass or TRVs all closed
How to Fix / Troubleshooting
Safety first: No immediate hazard if there is no smell of gas or burning, but efficiency and comfort are affected.
Homeowner checks:
- Ensure at least one radiator without a TRV is fully open to act as a bypass.
- Check room thermostat location (not above a radiator or in direct sunlight) and set it higher to test.
- Confirm that all TRVs are not set too low.
Engineer actions:
- Test room thermostat and wiring back to the boiler.
- Check NTC sensor readings and replace if out of range.
- Verify that a bypass valve is fitted and correctly set.
Reducing short cycling improves boiler life and fuel efficiency.
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Repair Difficulty
Medium
3/5
Required Part
Room Thermostat
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