Low
S.34 on Vaillant ecoTEC plus Aquaplus

Your boiler has detected very cold temperatures and is running its pump to prevent your pipes from freezing.

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.

Technical description

Frost protection mode

DIY fix possible

Ensure your heating is set to a schedule that prevents the house temperature from dropping too lowCheck that your external frost thermostat is not set too lowEnsure the boiler remains switched on at the mains so it can protect itself

Find a Gas Safe engineer
Search the official register →

Related fault codes

S.30View →S.31View →

Related guides you might find useful

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →