my sister in laws boiler has stopped producing hot water and had a look at it for her using the fault guide in the handbook.the flow from the taps seem normal but the led does not come on when a tap is turned on.i have check the flow switch and the microswitch works as it should when turning tap on and off.the book says pcb which is fine but because they are so dear i just wondered if the experts had any more tests i can do just to rule out any silly things.appreciate any help.i would hate to buy a bord and fit and find it was something else.many thanks kevin.