BoilerFaultCodesTechnical description
Automatic Air Vent Intermes, Ref. 02.05.010
What causes this fault?
This fault occurs when the automatic air vent fails to stay airtight or becomes blocked by debris and limescale buildup within the heating system. When this component stops functioning, air pockets can become trapped inside the boiler, causing the internal pump to struggle or the system to overheat. The most common reason is age-related wear on the internal float mechanism, which prevents it from purging air effectively.
This fault is more common in autumn when heating systems are turned back on after a long summer break, as stagnant water can cause the internal vent mechanism to seize or stick.
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.