Everything off but still hot water!

[chrisinwales]

can anyone help please? I've got a baxi back boiler system for my hot water and central heating which is controlled by a horstman amethyst 7 controller. At the moment with the 3 way switch in the off position and both the heating and water switches set to off, my boiler is still firing up and giving me hot water. The only way I can stop it is to isolate the mains supply from the horstman controller. Does this sound like a faulty controller or something more complicated?

 

[gas4you]

If this is a normal boiler and not a combi, I do not know the controller you list, then it will be the HW zone valve microswitch stuck on. You can check this with a multimeter in the wiring centre, turn off poer, remove orange wires, turn power back on and test HW valve orange wire for live with ptrogrammer off. If it is live then this proves the head has had it. Replace head.