High Lockout
F.11 on Vaillant ecoMAX 824E

Your boiler has stopped working because one of its internal temperature sensors has developed an electrical fault and is giving an incorrect reading.

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

Short circuit – return–NTC (< 130 °C) NTC defective | Cause: NTC– plug shorted to casing

What causes this fault?

This fault occurs when the sensor responsible for monitoring the temperature of the water returning to the boiler fails or develops an electrical short. The most common reason is that the sensor's internal insulation has broken down or the connecting wires have touched the metal casing, sending an incorrect electrical signal to the main control board.

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

F.01View →F.10View →

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