BoilerFaultCodesYour boiler's external temperature sensor is sending an incorrect signal, which usually means the system cannot adjust its heating based on the weather outside.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Outside temperature sensor error (S4)
What causes this fault?
This fault occurs when the boiler is unable to receive a reliable signal from the small sensor mounted on the outside of your property. The most common reasons are that the sensor’s internal components have corroded due to exposure to the elements, or the electrical wiring connecting the sensor to the boiler has become damaged or loose.
This fault is often more noticeable during autumn and winter when the boiler needs to calculate higher flow temperatures to keep the home warm.
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 E32 — no call-out fees, no surprises.
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