F2 = Flame present with burner off... boiler thinks it is lit when it shouldnt be. Would be either an electrode fault or "card" (circuit board)
F5 = air pressure switch fails to close within 60sec of turning the fan... basically something wrong with the air flow through the boiler, this may also cause your F2 fault.
The long and short of it is, its not something you can fix your self.
A3TDI
January 2009
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