Can you confirm where the terminals are that you are checking?
ok. thanks. your sytem may have been wired incorrectly and so is picking up a stray current.
do you have 2 x two port motorised valves ot 1 x 3 port motorised valve ,
just to let you know wiring probs can take a bit of sorting out. it will need a bit of patience on both sides, but i will stay with it till it is sorted.
your boiler may only need one wire going into it. a switched live to fire the boiler, this will come from the orange on the motorised valve and connection 1 (nc) cylinder stat
ok , thanks. in that case you should have 2 connentions out of your clock , one heating on, the other hot water on . check that apart from neutral, live,earth in these are the only 2 other wires out and the hot water off isnt wired up. do you have an s plan wiring diagram?
ok .you might have to trace the wiring all the way back from the fused spur to the clock and then hot water on to cylinder stat to hw valve to orange live to boiler. heating on to room stat to heating valve to boiler. sometimes with this sort of fault the only way to do it it is to basically start again and rewire. in this situation its usually easier because you never know what the sparky or heating engineer has done . There could be a fault with the valve aswell . might be woth swopping the heads and wiring and see if it makes a difference and if it does replace it
is it just the hot water valve flickering?