BoilerFaultCodesTechnical description
Boiler shut down due to air passing through the pump or system not correctly vented (monitors temperature rise across the heat exchanger).
What causes this fault?
This fault occurs when air bubbles get trapped inside the boiler’s internal pipework or the pump, preventing water from moving heat away from the burner. The most common reasons are a buildup of air after a repair, a leak in the system, or an automatic air vent that has become blocked with debris or limescale over time.
This issue often appears in autumn when the heating is turned back on after summer, as air can settle in the pipes during long periods of inactivity.
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.
Find a Gas Safe engineer
Search the official register →