F11
Ideal
NTC Sensor Circuit Error (General)
Heater shows F11 and will not operate, often after wiring work or rodent damage.
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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
Short between sensor wires, Broken harness to temperature sensors, Incorrect sensor fitted, Water ingress into connectors
How to Fix / Troubleshooting
Safety: Turn off power before handling wiring.
- Inspect all NTC connectors: Check flow, return, and DHW thermistor plugs at the control board. Ensure each is in the correct socket and fully seated.
- Look for moisture: Any signs of water inside the casing or on connectors must be addressed first. Identify and stop the leak before drying and reconnecting.
- Check harness routing: Ensure sensor cables are not trapped under the casing or rubbing on sharp metal edges.
- Reset: After correcting obvious issues, restore power and reset. If F11 persists, a technician should test each sensor and harness with a multimeter.
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Repair Difficulty
Hard
4/5
Required Part
Sensor Wiring Harness
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