BoilerFaultCodesSaunier Duval F5 Fault Code
The Saunier Duval F5 fault code means: your boiler has switched itself off because it has reached an unsafe temperature to protect the internal components from damage.. It appears on 6 Saunier Duval models in our database.
Technical description: Overheating fault
What causes the Saunier Duval F5 fault?
This fault occurs when the water inside the boiler gets too hot, causing a safety sensor to trip and shut the system down. The most common reasons are a pump failure that stops water from circulating or a buildup of sludge and debris that restricts flow through the heat exchanger.
This fault is more common when the heating is first turned on in autumn, as pump components can seize up after being idle throughout the summer.
DIY fix possible
Check that all radiator valves are fully open to allow water to circulateEnsure the boiler pressure gauge is between 1 and 1.5 barPress the reset button once to see if the fault clears after the system has cooled down
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Gas Safe Register →Saunier Duval models that show the F5 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Saunier Duval F5 fault code information on this page is sourced and cross-checked against the official Saunier Duval service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026