BoilerFaultCodesTechnical description
summer mode
What causes this fault?
This status occurs because the heating control or the thermostat has been set to provide hot water only, effectively turning off the central heating circuit. It is often triggered manually by a user switching to 'summer mode' or automatically when an outdoor sensor detects that the weather is warm enough to no longer require home heating. There is no mechanical failure; the boiler is simply following instructions to save energy by ignoring heating demands.
This code is most common during late spring and summer when homeowners intentionally disable their heating or when outside temperatures rise.
DIY fix possible
Locate the 'Mode' button or the heating temperature dial on the boiler control panel.Increase the central heating temperature setting to a level above the minimum (usually indicated by a radiator icon).The 'S.31' code should disappear and be replaced by a standard heating or hot water status code.