High Lockout
4.9 on Ideal Vogue Combi

Your boiler has lost its ability to measure the temperature of the water coming back from your radiators, often resulting in the system shutting down for safety.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Return Thermistor Fault

What causes this fault?

This fault occurs when the sensor responsible for monitoring the temperature of the water returning to the boiler begins sending incorrect data or stops communicating entirely. The most common reason is that the internal components of the thermistor have degraded over time or a wire has shaken loose, preventing the boiler from safely managing its heat output.

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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Related fault codes

4.8View →

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