A7
Worcester
Hot Water Temperature Sensor Error
Boiler displays A7, hot water temperature is erratic or incorrect, particularly on combi models.
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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
Misfitted Worcester DHW NTC, sensor out of calibration, wiring fault, scale build-up affecting sensor response
How to Fix / Troubleshooting
Safety first: Isolate power before removing the boiler front panel. Beware of hot water and surfaces.
Homeowner checks:
- Run a hot tap and observe if the temperature fluctuates wildly or is much hotter/colder than set.
- Reset the boiler once to see if the code clears.
Engineer checks:
- Confirm the DHW NTC is firmly seated in its pocket or clipped correctly to the pipe.
- Measure sensor resistance at known temperatures and compare with Worcester data.
- Inspect for limescale around the sensor location; descale if necessary.
- Replace the DHW NTC if readings are unstable or out of range.
Correct sensor placement and condition are essential for safe hot water temperature control.
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Repair Difficulty
Medium
3/5
Required Part
DHW Temperature Sensor (NTC)
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