BoilerFaultCodesTechnical description
Indicates the fan is not operating or the air pressure switch has failed to operate.
What causes this fault?
This fault occurs when the boiler's safety sensors cannot confirm that harmful exhaust gases are being safely blown out of the flue. The most common reason is that the internal fan has seized or the air pressure switch, which acts as a safety gatekeeper, has failed to detect the required airflow. In some cases, a small piece of debris or a perished rubber tube inside the unit is enough to prevent the system from starting.
This issue can be more frequent during periods of high winds, as strong gusts can occasionally create back-pressure in the flue that interferes with the air pressure switch.
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.