I have a Horstmann timer controlling a fully pumped sytem with a
mid-position valve. If HW and CH are selected and running, then switching CH
off does not cause the valve to move even at the end of the on/off cycle.
The only solution is to disconnect the mains from the system sometime during
the off period when the spring moves the valve to the correct HW-only
position.
Is this a wiring error on my system or a problem with this type of valve?.
Can anyone help with a solution?

Alan Booth