BoilerFaultCodesTechnical description
TEMPERATURE LIMITER. CONTROLLED BY THE HEATING THERMISTOR ON FLOW PIPE: CHECK HEATING THERMISTOR (MAY BE UNCLIPPED) OR THREE WAY VALVE FAULTY. FAULTY PUMP. LOW HEATING FLOW RATE.
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the water temperature has exceeded a safe limit, causing the system to shut down for safety. The most common reason is a lack of water circulation, often caused by a failing pump or a stuck valve prevented water from leaving the boiler. It can also be caused by a simple sensor failure or a loose clip providing an inaccurate temperature reading.
This issue often surfaces when you first turn the heating back on in autumn, as internal moving parts like the pump or three-way valve can seize up after being idle throughout the summer.
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.