Boiler shows F1, often indicating a flow sensor or pump-related issue, heating may be weak or non-existent.

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

Stuck Worcester flow switch, blocked flow sensor, pump not circulating, wiring fault to flow sensor

Safety first: Isolate power and allow the boiler to cool before touching pipework.

Homeowner checks:

Ensure all radiator valves are open and that there are no obvious isolation valves closed near the boiler.
Check system pressure and top up if low.

Engineer checks:

Inspect the flow sensor or flow switch for debris or sticking; clean or replace as needed.
Verify pump operation and bleed any air from the pump housing.
Check wiring continuity between the flow sensor and PCB.

Restoring proper flow detection is essential for safe boiler operation.

Medium 3/5

Flow Sensor / Flow Switch

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