Low
S.31 on Vaillant Thermocompact

Your boiler is currently set to summer mode, which means it is turned off for household heating and is only active for hot water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

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.

What the manual says

Manufacturer manual

Summer mode (heating control knob in off position)

From this model's manual
Verified against the Vaillant Turbomax Plus 824 828e installation & service manual, page 38.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Locate the heating control dial on the front of your boiler.Turn the dial clockwise to your desired temperature setting.The boiler will now switch to winter mode and begin providing heating.

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