Medium

Return Thermistor Fault on Keston Combi 30

Your boiler is temporarily unable to accurately measure the temperature of the water returning from your radiators.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026

What the manual says

Manufacturer manual

Return Thermistor

From this model's manual

Verified against the Keston/Keston Combi 30 installation & service manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

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All 14 fault codes on the Combi 30

Seeing a different code? Every code this model can display, in one place.

Boiler Type Card Fault Fan Fault Flame Loss Flow Thermistor Fault Ignition Lockout Lockout 6 Low Mains Voltage Low Water Pressure Outside Sensor Fault Overheat Lockout PCB Fault PCB Replacement Too Many Resets

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