Sympton was control panel dead, with no lights showing on user controls, and no response to control panel on/off switch despite mains power and fuse being in good working order.
Boiler engineer used multimeter to check that all electrical values were correct.
First part of the solution was to change the PCB printed circuit board.
This reinstated power to consumer control panel, and pump operated normally. However, fan and boiler remained out of order, and display showed H 4.
Fault-finding frame 87 is not complete: replace PCB alone does not resolve the problem. It is necessary to insert jumper links in the top right of the new PCB plastic case, in the same pattern as jumper leads in the top right of the old PCB plastic case.
Boiler then resumed normal operations.
mkpaul, January 2015
