Potterton EP2000 heating system

[clivemg]

Can anybody help with this one. I have a heating / hot water system controlled by a Potterton EP2000 programmer with a Honeywell V4073A1039 3 position diverter valve. When the hot water system is operating the 3 position valve does not always revert to the correct position and allows hot water into the radiators. I have watched the 3 position valve and when this happens, the valve tries to move to the hot water only position but immediately goes back to the heating / hot water position and continually cycles between the two, on the microswitches.
Does anybody know whether it would be the controller that is at fault or the diverter valve?

 

[chrishutt]

Diverter valve fault. If you do a search on mid position valves you'll find that the operation of these was recently discussed in detail, complete with a set of circuit diagrams! You might be able to replace just the actuator part of the valve, or even repair if you understand enough about the electrics.

 

[clivemg]

Many thanks for the reply. The information regarding operation of the diverter was very illuminating! What appears to be happening then, is that a demand for HW / CH has occured (I don't know why because this happens with CH switched off as well) which motors the valve to the mid position, but when the microswitches are made there is no holding current to keep it there, so the valve tries to revert back to the HW only position and so on!
Do you still think it would be the diverter valve in view of this?