Low
S.5 on Vaillant ecoTEC exclusive 838

Your boiler is pausing briefly because it has finished its heating cycle or has reached the required temperature and is now cooling down internal components.

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

Fan and water pump return water

From this model's manual
Verified against the Vaillant/Vaillant Ecotec Exclusive 74c27d 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

Wait for 5-10 minutes as this is often a normal part of the boiler's operationCheck that your room thermostat is not set lower than the current room temperatureEnsure all radiator valves are open to allow heat to dissipate

Find a Gas Safe engineer
Search the official register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like S.5: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

S.0View →S.7View →S.8View →

All 71 fault codes on the ecoTEC exclusive 838

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

conF.0F.1F.10F.11F.13F.20F.22F.23F.24F.25F.27F.28F.29F.32F.49F.61F.62F.63F.64F.65F.67F.70F.71F.72F.73F.74F.75F.76F.77P.0P.1P.2P.5P.6S.0S.1S.2S.3S.4S.6S.7S.8S.10S.11S.13S.14S.15S.16S.17S.20S.21S.23S.24S.25S.26S.27S.28S.30S.31S.32S.34S.36S.41S.42S.53S.54S.96S.97S.98

Related guides you might find useful

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →

Boiler service cost

What a UK service costs and what a proper one includes.

Read →