Boiler shows F10, will not start, temperature reading may be abnormal
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Isolate power before removing the boiler front panel. System water may be hot; allow to cool before touching pipework.
- Reset the boiler: Perform a reset. If F10 reappears immediately, the sensor or wiring is likely faulty.
- Visual inspection: Locate the flow temperature sensor (NTC) on the flow pipe from the heat exchanger (refer to manual). Check that the plug is firmly connected and wiring is not damaged.
- Check for leaks: Look for any water leaks around the sensor pocket that could have damaged the sensor or connector.
- Engineer tasks:
- Measure the NTC resistance at ambient and compare with Glow-worm charts.
- Inspect wiring continuity back to the PCB.
- Replace the flow NTC if readings are out of range.
Replacing an NTC is usually straightforward but may require draining a small amount of water; if unsure, use a professional.
Repair Difficulty
Required Part
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