High Lockout
Flow Thermistor Fault on Potterton Performa SL HE 9 2

Your boiler has switched itself off because the internal temperature sensors are giving conflicting or unusual readings, meaning it cannot safely regulate the heat.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Lockout Burner Mains - Automatic Flow Thermistor Fault (Thermistors reading outside of limits or difference between readings outside of limits)

What causes this fault?

This fault occurs when the sensors responsible for monitoring the temperature of the water leaving the boiler fail to report consistent data. The most common reason is that the internal components of the sensor have degraded over time, though it can also be caused by loose wiring or a communication error within the main control board.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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