fault prob'mechanical ,if I remember the fault finding chart is all electrical based,if you have the manual you'll know what I mean..(do you have 240v between terminal ..blah,blah). 9 times out of 10 its the diaphragm on the diverter valve . When a hot tap is turned it operates the diaphragm which push's a spindle that operates a fulcrum arm and micro switch to bring on the burner when a tap is on. you should actually be able to see this operate whenever a tap is turned on & off . Sited bottom front left of boiler below pump
papmc, February 2009
