FLOW THERMISTOR FAULT High

Johnson Starley FLOW THERMISTOR FAULT Fault Code

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

Your boiler's temperature sensor is reporting an error, which means the system cannot accurately track how hot the water is and has stopped running as a safety precaution.

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

Typical repair cost for the Johnson Starley FLOW THERMISTOR FAULT fault is £95-£170 including labour.

Also written as FLOWTHERMISTORFAULT — same fault.

The Johnson Starley FLOW THERMISTOR FAULT fault code means: your boiler's temperature sensor is reporting an error, which means the system cannot accurately track how hot the water is and has stopped running as a safety precaution.. It appears on 1 Johnson Starley model in our database.

Technical description: Flow thermistor fault involves checking wiring, connection to the low voltage 9 way connector X5 on the PCB, and thermistor resistance

Typical repair cost £95-£170 (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 FLOW THERMISTOR FAULT fault code

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

J32 System ET Repair: £95-£170

Source

Johnson Starley FLOW 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