F.89 High

Vaillant F.89 Fault Code

Also written as F89 — same fault.

The Vaillant F.89 fault code means: your boiler's main internal pump is not speaking correctly to the control board, preventing the system from circulating heat.. It appears on 22 Vaillant models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Incorrectpumpdetected: Unsuitablepumpconnected,PWMplugnotpluggedinorhascome loose,multipleplugonthePCBnotpluggedincorrectly,interruptionin cableharness,electronicsdefective

What causes the Vaillant F.89 fault?

This fault occurs when the boiler's brain loses communication with the internal pump that pushes hot water around your radiators. It is usually caused by a loose electrical connection, a damaged wiring harness, or the pump itself failing to send the correct signal back to the control board. Without this two-way communication, the boiler shuts down as a safety precaution to prevent overheating.

This fault is more common in autumn when heating systems are turned on for the first time after summer, as pump components can seize or electrical contacts can fail during long periods of inactivity.

Typical repair cost £180-450 (including labour)

Engineer required

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

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Vaillant models that show the F.89 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vaillant F.89 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026