Low
S.34 on Vaillant ecoTEC exclusive 627 VU 256/5-7

Your boiler has noticed the temperature is very cold and has automatically turned itself on to prevent the internal 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.

What the manual says

Manufacturer manual

Heating mode: Frost protection / Frost protection mode active

From this model's manual
Verified against the Vaillant/Vaillant Vaillantpro 0020193966 04 Ecotec Exclusive System Installation I installation & service manual.
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

No action is required; this is a normal safety function.The boiler will stop this mode automatically once the internal water temperature rises sufficiently.Ensure your external condensate pipe is not frozen if the weather is extremely cold.

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Related fault codes

S.24View →

All 72 fault codes on the ecoTEC exclusive 627 VU 256/5-7

Seeing a different code? Every code this model can display, in one place.

F.00F.01F.02F.03F.10F.11F.12F.13F.20F.22F.23F.24F.25F.26F.27F.28F.29F.32F.33F.35F.42F.49F.55F.56F.57F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.77F.78F.80F.81F.82F.83F.84F.85F.90F.94S.36S.37S.39S.40S.41S.42S.46S.53S.54S.55S.56S.57S.58S.59S.76S.86S.88S.92S.93S.96S.97S.98S.99

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