Medium
D.14 on Vaillant Atmomax

Your boiler is struggling to control the speed of the pump that moves hot water around your pipes and radiators.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Pump speed target value

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →

Related fault codes

F.20View →F.24View →

Related guides you might find useful

Radiators cold at the bottom

Sludge build-up — needs flushing, not bleeding.

Read →

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →