Boiler shows F.74, pressure reading too high or sensor short circuit

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Shorted pressure sensor, Moisture in connector, Shorted wiring harness, PCB fault

Safety: Check the actual system pressure on the gauge. If genuinely high (>2.5–3 bar), do not ignore.

Relieve excess pressure: Bleed radiators to reduce pressure to 1.0–1.5 bar. Do not repeatedly overfill the system.
Inspect sensor and wiring: With power off, unplug the sensor and check for water in the connector. Dry and refit if necessary.
Engineer diagnosis: If F.74 persists with correct pressure, the sensor or PCB may need replacement.

Medium 3/5

Water Pressure Sensor

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