F12 INDICATES A USER INTERFACE FAULT . BEFORE YOU REPLACE THE BOARD YOU MAY WANT TO CHECK FOR ANY LOOSE WIRES AND / OR WATER INGRESS THROUGH THE VARIOUS MINI PLUGS SITUATED THROUGHOUT THE INTERNAL COMPONENTS OF THE BOILER . I FOUND MINE WAS LEAKING FROM THE FLOW SENSOR WHICH WAS CAUSING WATER INGRESS INTO THE MINI PLUG SITUATED ON THE TOP OF THE FLOW SENSOR , THIS WAS CAUSING THE F12 FAULT TO APPEAR . UPON REPLACING THE FLOW SENSOR THE BOILER WORKED PERFECTLY .
GARY WHITEHOUSE, December 2009
