BoilerFaultCodesTechnical description
Three way valve test
What causes this fault?
This fault occurs when the boiler's internal computer tries to move the diverter valve to switch between heating and hot water, but the movement isn't detected correctly. The most common reason is that the valve has become stuck due to a buildup of debris in the system or the small electric motor that moves the valve has failed.
This fault is frequently seen at the start of autumn when the heating is turned back on after being idle all summer, which can cause internal moving parts to seize.
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 →