Have been to see the above today. Have tried disconnecting thermistors overheat fan and gas valve and have tested resistance and continuity of the loom. The fault persists is there anything anyone out there knows causes this or causes the PCB to fail with this error. Disconnecting the fan caused the board to emit a high pitched whistle like faulty capacitors can make. No signs of charing on the board and it is bone dry. Disconnecting the other components caused the error message to change to an f# relating to that component. When the loom is all connected it reverts to f13 which is suppose to indicate connection or loom fault.