If you remove the casing of the boiler, switch the electricity off, then undo the screw holding the PCB board assmbly to the boiler, swing this assembly clear of the boiler, you can then see the square box which is the diverter valve. You can try moving the diverter valve by hand, or, with the PCB assembly still swung out, switch the boiler on, and switch the central heating on and watch to see if the diverter valve operates. ENSURE YOU DO NOT TOUCH ANY OF THE WIRING - YOU COULD GET A SHOCK. If you cannot see the valve working, or are not sure if it is working, call a qualified heating engineer out. MAKE SURE YOU SWITCH OFF THE ELECTRICITY SUPPLY TO THE BOILER BEFORE CAREFULLY SWINGING BACK THE HINGED ASSEMBLY THAT HOUSES THE PCB CONTROL BOARD. wATCH THAT YOU DON'T PINCH ANY WIRES.
Phil Edwards, November 2006
