E11
Potterton
Return Thermistor / NTC Sensor Fault
Boiler intermittently locks out with E11, especially when heating is on for long periods
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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 return NTC sensor, Loose sensor connection, Damaged wiring harness, PCB sensor circuit fault
How to Fix / Troubleshooting
Safety first: Isolate power before removing covers.
User checks:
- Reset the boiler and monitor if the error appears only under certain conditions (e.g., long heating cycles).
Engineer checks:
- Locate the return NTC sensor on the return pipe to the boiler.
- Measure resistance at ambient and operating temperatures; compare with Potterton charts.
- Inspect wiring and connectors for corrosion or mechanical damage.
- Replace the return NTC sensor if readings are inconsistent or out of range.
- If sensor is OK, test continuity to PCB and evaluate PCB input.
Correct sensor diagnosis prevents unnecessary PCB replacement.
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Repair Difficulty
Medium
3/5
Required Part
Return NTC Thermistor
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