High Lockout
AL73 on Vokera Mynute Vhe

Your boiler has detected a problem with the sensor that monitors the water temperature returning from your radiators, preventing the system from heating effectively.

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 boiler's internal computer stops receiving a reliable signal from the sensor that monitors the temperature of the water returning to the unit. The most common reason is that the sensor itself has worn out and failed, or the electrical wiring connecting it to the main control board has developed a loose connection or a short circuit.

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

AL71View →AL79View →

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