BoilerFaultCodesYour boiler is trying to start up but is detecting a problem with how it vents waste gases, causing it to shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Lighting Sequence - Fan/APS
What causes this fault?
This fault occurs when the boiler's internal safety sensor fails to detect enough airflow to safely carry exhaust gases outside. The most common reasons are a buildup of dirt inside the fan, a perished rubber tube, or a blockage in the flue pipe that prevents the system from breathing correctly.
This issue often surfaces during the first cold spells of autumn when the fan and pressure switch are forced to work harder after sitting idle over the summer.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
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