F.80 Medium

Vaillant F.80 Fault Code

Also written as F80 — same fault.

The Vaillant F.80 fault code means: your boiler is having trouble communicating with the temperature sensor in your hot water storage unit, meaning your water might not heat up correctly.. It appears on 1 Vaillant model in our database.

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: Fault:actoSTORinletsensor OnlyinconjunctionwithF.91 NTCdefective,NTCcabledefective,defectiveplugconnectiononNTC, defectiveplugconnectionontheactoSTORelectronics Sensorplughasshorttoearthtothehousing,shortcircuitincablehar- ness,sensordefective
Typical repair cost £120-250 (including labour)

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 for a qualified engineer in your area.

Gas Safe Register →

Vaillant models that show the F.80 fault code

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

Source

Vaillant F.80 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