High Lockout
F.74 on Vaillant ecoTEC exclusive

Your boiler has detected an electrical issue with its internal water pressure sensor, meaning it cannot accurately tell if there is enough water in the system to run safely.

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

Signal water pressure sensor in the wrong range (too high): Line to water pressure sensor has a short-circuit at 5V / 24V or internal fault in water pressure sensor

What causes this fault?

This fault occurs when the boiler's control board receives an electrical signal from the water pressure sensor that is outside of its normal operating limits. The most common reason is an internal electronic failure within the sensor itself, or a wiring issue where a moisture leak or loose connection has caused 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

F.73View →F.22View →F.24View →

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