Firstly the timer red light was flashing and loudly clicking. Then I found a leak on the flow going into the heat exchange nut through to top section. Then i found that the mains power was fused. Next i found that the PCB was blown. I repaired the leak, fit a new timer, fit a new PCB (red not green), fit a new ch Thermistor.
Wired a plug to boiler and ran an extension.
Switched the boiler on. Green light on, red light on, timer red light on, nothing else working. Young couple with new baby no hot water, no central heating.
NAS, January 2014