BoilerFaultCodesYour boiler's internal safety fan system is failing to signal that it is safe to ignite, preventing the heating from starting.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: APS Stuck Fault
What causes this fault?
This fault occurs when the boiler's internal safety sensor, the Air Pressure Switch, fails to detect the correct airflow required for a safe ignition. It is often caused by a buildup of dust in the fan, a perishing rubber tube, or a blockage in the small plastic venturi that monitors the exhaust gases.
This issue frequently surfaces during the first cold spell of autumn when the fan and switch are forced to work harder after sitting idle throughout 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
A boiler cover plan would cover faults like Lockout (Red) Off, Burner (Green) On, Mains (Green) On — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Potterton Performa SL HE 9 2 is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.