Boiler shows E27, external sensor or weather compensation not detected or faulty

Safety: Isolate power before accessing control wiring.

User checks:

• If an outdoor sensor is fitted, note any damage to the sensor housing or cable and inform the engineer.

Engineer checks:

• Locate the Keston outdoor sensor and inspect for physical damage or water ingress.
• Measure sensor resistance and compare with temperature/resistance chart; replace if out of range.
• Check continuity and polarity of the sensor cable back to the boiler terminals.
• Confirm correct configuration of weather compensation in the boiler settings.