BoilerFaultCodesTechnical description
Heating flow thermistor fault
What causes this fault?
This fault occurs when the internal sensor responsible for tracking the temperature of the water sent to your radiators fails or provides an illogical reading. The most common reason is that the sensor has physically degraded or developed an electrical short, meaning the boiler can no longer verify if it is operating at a safe temperature. In some cases, loose or damaged wiring between this sensor and the main control box can also trigger the error.
This fault is slightly more common in winter when the boiler is running at higher temperatures for longer periods, which places more thermal stress on the electrical components.
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.