BoilerFaultCodesWhat the manual says
Manufacturer manualInsufficient water pressure; Air in boiler. Appears if the pressure in the boiler is low.
What causes this fault?
This fault occurs when the internal pressure sensor detects that there isn't enough water in the system to operate safely. The most common reasons are a slow leak in the pipework, air trapped inside the boiler's heat exchanger, or simply needing a top-up after bleeding your radiators.
This code often appears in autumn when homeowners bleed their radiators for the first time in months, causing the system pressure to drop.
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 04: no call-out fees, no surprise bills.
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