F.02 High

Vaillant F.02 Fault Code

Also written as F02 — same fault.

The Vaillant F.02 fault code means: your boiler is having trouble sensing the temperature of your hot water supply, which means it has stopped providing hot water to prevent overheating.. It appears on 3 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: DHW-NTC: NTC broken; NTC cable broken; Defective connection at NTC; Defective connection at electronics | DHW- NTC cable defective/ broken NTC faulty
Typical repair cost £120-220 (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.02 fault code

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

Source

Vaillant F.02 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