Checked that again - definitely 90v on orange and white when neither is calling (but power is on), and the orange is disconnected.
Reconnect the orange and both orange and white drop to zero - presumably because the orange is now "earthing" through one of the other connections (though not sure which and how!). Guess the fact that the white also drops shows that both must be connected inside the actuator?
Regarding the lever, I think that is is actually operating correctly - I think I'm right in saying it should only have resistance if there is no voltage on white or grey, so only when the power is off or HW is on by itself. When the CH is on, or has been on more recently than HW, it will be floppy, and this is the case most of the time, henc it normally being floppy.
So, one way or another, I don't think I'm much nearer finding the problem - valve seems to behave as expected. But once again, this testing has all been done while the CH has been working fine - it's started behaving all evening. Sod's law, but with the obvious benefit that I have a warm house now!
Reconnect the orange and both orange and white drop to zero - presumably because the orange is now "earthing" through one of the other connections (though not sure which and how!). Guess the fact that the white also drops shows that both must be connected inside the actuator?
Regarding the lever, I think that is is actually operating correctly - I think I'm right in saying it should only have resistance if there is no voltage on white or grey, so only when the power is off or HW is on by itself. When the CH is on, or has been on more recently than HW, it will be floppy, and this is the case most of the time, henc it normally being floppy.
So, one way or another, I don't think I'm much nearer finding the problem - valve seems to behave as expected. But once again, this testing has all been done while the CH has been working fine - it's started behaving all evening. Sod's law, but with the obvious benefit that I have a warm house now!
