If it sparks, then does not light, then he may be right - gas valve or pcb.
He needs to watch it - there are 2 different pcb's for this boiler depending on which gas valve is in it (show him this answer, he will be grateful):
Dungs valve (solenoids at front, 3 pairs of wires connecting it) needs 8748 300 488 0 board.
Prettl valve (older version, solenoids at back, 2 pairs of wires) needs 8748 300 417 0 board.
Remember to remove the code plug from old pcb to put it in the new one.
Bunslinger, April 2009
