Valiant eco tech 630 no hot water

[MrStark]

Hi, first post. Engineer is booked for 5th of June. But just would like some clues. I’ve read the other posts and the zone valve is likely culprit still.

ch fine
Zone valve for hw doesn’t move
I do hear a click in the nest heat sync when I choose hot water.
If I open and lock the zone valve for hw.
I get hot water when the ch fires up .
But not if I just choose hw
No hot water symbol on valiant (never noticed one).
Q:what causes hw to fire up. ?
Q: any tests I can do to locate the issue fully
Q: does it sound like it is “just” the valve ?
Q: is it ok to leave zone. Valve for hw locked open till engineer ?
Cheers

 

[Harry Bloomfield]

Most likely a failed valve actuator - motorised head part of the valve.