BoilerFaultCodesYour boiler is currently in summer mode, which means it will provide hot water but has temporarily disabled your central heating.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical 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.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like S.31 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Glow-worm Ultrapower sxi is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.