BoilerFaultCodesTechnical description
Header Thermistor (T1) Error – for cascade and hybrid
What causes this fault?
This fault occurs when the main temperature sensor responsible for monitoring the shared water supply becomes unresponsive or provides an impossible reading. The most common reason is a physical failure of the internal sensing element, though it can also be triggered by loose or corroded electrical connections between the sensor and 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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