BoilerFaultCodesYour boiler has detected a problem with the sensor that measures hot water temperature, which often means your hot water may be cold or inconsistent.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: DHW temperature sensor error (S3)
What causes this fault?
This fault occurs when the boiler's control board loses communication with the sensor responsible for monitoring your hot water temperature. The most common reason is that the internal components of the sensor have failed due to age, or the electrical connection has become loose or corroded. Because the boiler can no longer tell how hot the water is, it shuts down as a safety precaution to prevent overheating.
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like E31 — no call-out fees, no surprises.
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