Your boiler has detected a fault with the sensor that monitors water temperature returning from your radiators, preventing the system from heating up properly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: The heating return thermistor is short circuited.
What causes this fault?
This fault occurs when the sensor responsible for measuring the temperature of the water coming back from your radiators fails or develops an electrical fault. The most common reason is that the internal components of the sensor have degraded over time or moisture has compromised the electrical connection, causing it to send a faulty signal to the main control board.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like 32 — no call-out fees, no surprises.
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