F39 Low

ECA F39 Fault Code

The ECA F39 fault code means: your boiler is having trouble communicating with the sensors that monitor the temperature outside, which can prevent it from heating your home efficiently.. It appears on 3 ECA 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 (blocking) — outdoor temperature sensor may be defective; press Reset; if persists notify ECA authorised service
Typical repair cost £90-160 (including labour)

DIY fix possible

Locate the Reset button on the boiler control panel.Press and hold the Reset button for 3 to 5 seconds.Wait to see if the error code clears and the boiler restarts normally.

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ECA models that show the F39 fault code

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

Source

ECA F39 fault code information on this page is sourced and cross-checked against the official ECA service / installation manuals for each affected model.

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