In an earlier contribution to this discussion,
Andy Johnson wrote:

I'm not sure what make the valve is - I can't see any identifying
marks on the body of the value, but access is rather cramped. Also,
someone (not me) has painted it. The metal seems like plain brass (no
zinc finish).

The motor is a synchron motor. About 1 1/2" high. Round on the top
and tear-drop shaped on the base with a small toothed wheel emerging
slightly off-centre.
It looks like this:
http://www.screwfix.com/sfd/i/cat/84/p1055284_l.jpg. It sits under a
metal cover above the valve.

Are you saying that when the valve opens fully it trips the
microswitch which turns on the pump and boiler? If so, would it make
sense to disconnect the microswitch from the junction box and use a
continuity tester to see if trips when I turn on the hot water? Or am
I still not understanding?

Andy

You're on the right lines. See my other post. If it's a Honeywell valve (and
probably if it isn't!) it's the grey and orange wires you need to be looking
at. The internal contacts (micro-switch) should connect these togther when
the valve is open. So you could disconnect the remote end of these wires and
then use a continuity tester between them. There's probably a junction box
in the airing cupboard with all the connections in. [But be careful working
on mains electrics - and get help unless you're sure what you're doing!]
--
Cheers,
Set Square
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