No Hot Water / Heating - New motorised valve

We had a problem with out central heating - ie it went off when the hot water came on and we could only have one or the other

My cousin who supposedly knows about these things said pump was fine it was the diverter valve we only needed a new actuator

So a few months later (yesterday) got the new bit as its getting cold, fitted it and hot water was fine, upstairs rads came on after letting some air out but not downstairs, had to go out so was going to do them today

Got home today and when i try and turn the heating or the hot water the boiler doesnt come on and so neither fo they

Have we done anything obviously wrong / are we supposed to do something else other than changing it?

Or has something else gone? bearing in mind they were working yesterday

It might help if you could identify the motorised valve and the boiler. Mid position motorised valves can be tricky to wire up correctly so the first question is "are you sure that it's wired up correctly?".

The OH did it - its a Sunvic SD2701 actuator identical to the one that came off, he took one wire out at a time and replaced it with the new ones to make sure he got them all in the right place

As i say after fitting it worked fine - it stopped the next day would wiring not mean it didnt work at all ?

Have you checked that it is not just a loose wire, or one that has fell out?

Remember, just because something is new does not make it work