Set Square,

Thanks for replying - you've made a lot of things clearer. And you're
right. I have two two-way valves.

I'm not clear what the 'volt-free' contacts are. Is this the
microswitch in the motor housing that John mentioned, or is it part of
the valve itself? I removed the motor cover, and unscrewed and
lifted-out the motor, and I could see a green plastic microswitch
underneath with a kind of cam that nudges it as the valve turns. Is
this what you mean?

Andy