BoilerFaultCodesTechnical description
Communication fault - extension kit for mixer circuit M2. Mixer M2 continues to move
What causes this fault?
This fault occurs when the boiler's main brain loses its connection with the electronic controller that manages your underfloor heating or a specific radiator zone. The most common cause is a wiring issue between the units or a component failure within the secondary control kit, which prevents the boiler from knowing how to correctly adjust the water temperature for that zone.
This issue is more frequently noticed during the transition into autumn or winter when the heating is first switched on and these secondary circuits are required to operate for the first time in months.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.