BoilerFaultCodesKeston E43 Fault Code
The Keston E43 fault code means: your boiler has detected an electrical fault with the internal sensor that monitors the temperature of the water returning to the unit, causing it to shut down for safety.. It appears on 9 Keston models in our database.
Technical description: Return sensor short circuit – check connections to return sensor
What causes the Keston E43 fault?
This fault occurs when the boiler's control board receives an incorrect electrical signal from the sensor that monitors the temperature of the water coming back from your radiators. The most common reason is that the sensor has suffered an internal electrical failure or the wiring connecting it to the main board has become damaged or loose.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Keston models that show the E43 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston E43 fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026