F6 Low

Heatline F6 Fault Code

The Heatline F6 fault code means: your boiler is having trouble readng the temperature outside, which it usually uses to adjust how hard it needs to work to heat your home.. It appears on 3 Heatline models in our database.

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.

Technical description: Outdoor Temperature Sensor Fault
Typical repair cost £90-160 (including labour)

DIY fix possible

Turn the boiler power switch to offWait 30 secondsTurn the power back on and press the reset button

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Heatline models that show the F6 fault code

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

Source

Heatline F6 fault code information on this page is sourced and cross-checked against the official Heatline service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026