4A High

Buderus 4A Fault Code

The Buderus 4A fault code means: your boiler has detected that the water inside is getting much too hot, so it has shut down to prevent damage.. It appears on 1 Buderus model 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: Blinking fault code: Flow sensor exceeds 105 °C
Typical repair cost £120-350 (including labour)

DIY fix possible

Check that all radiator valves are fully openEnsure the boiler pressure gauge is between 1.0 and 1.5 barBleed all radiators to remove trapped airPress the reset button once the boiler has cooled down

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Buderus models that show the 4A fault code

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

Source

Buderus 4A fault code information on this page is sourced and cross-checked against the official Buderus service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026