RETURN THERMISTOR FAULT High

Johnson Starley RETURN THERMISTOR FAULT Fault Code

Q: What does the Johnson Starley RETURN THERMISTOR FAULT fault code mean?

Your boiler has detected an issue with the sensor that monitors the temperature of the water returning to the unit, causing it to shut down to prevent damage.

Q: How much does it cost to fix Johnson Starley error code RETURN THERMISTOR FAULT?

Typical repair cost for the Johnson Starley RETURN THERMISTOR FAULT fault is £95-175 including labour.

Also written as RETURNTHERMISTORFAULT — same fault.

The Johnson Starley RETURN THERMISTOR FAULT fault code means: your boiler has detected an issue with the sensor that monitors the temperature of the water returning to the unit, causing it to shut down to prevent damage.. It appears on 1 Johnson Starley model in our database.

Technical description: Check the resistance using a suitable multi-meter connected across the thermistor’s terminal pins

Typical repair cost £95-175 (including labour)

Engineer required

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

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Johnson Starley models that show the RETURN THERMISTOR FAULT fault code

Click a model for the full fault code list and model-specific repair notes.

J32 System ET Repair: £95-175

Source

Johnson Starley RETURN THERMISTOR FAULT fault code information on this page is sourced and cross-checked against the official Johnson Starley service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026