BoilerFaultCodesYour boiler has developed a recurring problem with how it clears exhaust fumes and has locked itself out for safety after multiple failures.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Fault F05 generated 5 times within the last 24 hours – possible error with the air pressure switch
What causes this fault?
This fault occurs when the boiler detects a persistent issue with the air pressure switch, specifically after it has failed to operate correctly five times within a single day. The most common reason is a blockage or moisture in the small sensing tubes, or a mechanical failure within the fan assembly that prevents exhaust gases from being cleared safely. Because the fault has happened repeatedly, the boiler shuts down entirely to prevent the risk of unsafe operation.
This fault is more common during periods of high wind or extreme cold, as external gusts can disrupt pressure readings and freezing temperatures can cause moisture to build up inside the sensing tubes.
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 A15 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.