BoilerFaultCodesFerroli F43 Fault Code
The Ferroli F43 fault code means: your boiler has stopped working because water is not moving through it properly or there is trapped air causing it to overheat.. It appears on 9 Ferroli models in our database.
Technical description: Exchanger protection activation – no system circulation air in system
What causes the Ferroli F43 fault?
This fault occurs when the boiler detects that heat is not being carried away from the heat exchanger fast enough, causing it to reach a dangerously high temperature. The most common reasons are a failed pump that isn't pushing water around, or a buildup of air and sludge that is blocking the flow within the pipes.
This issue is more frequent in autumn when heating systems are switched back on after a summer of inactivity, which can cause internal pump components to seize.
DIY fix possible
Check that your system pressure is between 1 and 1.5 bar on the pressure gaugeBleed all radiators in your home to remove trapped airEnsure all radiator valves and external isolation valves are fully open
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Ferroli models that show the F43 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ferroli F43 fault code information on this page is sourced and cross-checked against the official Ferroli service / installation manuals for each affected model.
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Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026