Motorised valve heads (diverter valves) Reasons a motorised valve head will fail to start: Motorised valve head lead faulty Burnt out motor windings Motor axle/spindle seized Faulty printed circuit board These devices are energised or de energised (via the printed circuit board) to operate a motorised axle/spindle. The movement of the motorised spindle communicates with the diverter valve via a bobbin assembly, controlling the path of heated primary water, either to the secondary plate exchanger or to the central heating circuit. To test a motorised valve head lead: 240 V LIVE TEST   Lead: Set multimeter to correct voltage scale and check at connections <table “class=”footable”> Central heating on:240Vac between connections 1 and 2 25Vac-35Vac between connections 2 and 3Hot water on:240Vac between connections 2 and 3 25Vac-35Vac between 1 and 2. Incorrect voltages maybe faulty printed circuit board or lead – needs further investigating. Correct voltages but motor axle not moving – replace motorised valve head To test motorised valve head: Set multimeter to Ohms scale and measure coil resistance: 0 Ohms between connections 1 and 3 9.6 K Ohms between connections 1 and 2 (resistance may vary) 9.6 K Ohms between connections 1 and 3 (resistance may vary) Motor axle retracts on hot water or hot water pre-heat facility – ok Motor axle visible on heating –ok…