BoilerFaultCodesWhat the manual says
Manufacturer manualNo pressure rise was detected on turning on the pump | Water pressure sensor or/and pump defective, Air in the heating system, quick bleeder defective, Too little water in appliance; check adjustable by-pass; connect external expension vessel to return
What causes this fault?
This fault occurs when the boiler's internal computer fails to see a small 'jump' in water pressure that should happen every time the pump starts spinning. The most common reasons are a pressure sensor blocked with sludge or a pump that has seized up after a period of inactivity, meaning the system can't verify that water is circulating safely. In some cases, it can also be caused by the system pressure simply being too low for the sensor to register any movement.
This issue is frequently seen at the start of autumn when homeowners turn their heating back on for the first time, as the pump can seize up after sitting idle all summer.
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.
Avoid the next call-out bill
A cover plan would handle faults like F.75: no call-out fees, no surprise bills.
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