Drayton ZA5 valves and Danfoss room thermostats

[pete60]

Any help appreciated. I think I have a sticking valve, stays open when thermostat switches off. Its under the floor and carpets so before I lift it all I'm trying to understand as much as I can.
Hopefully I will be able to lubricate and loosen up the spindle and solve problem that way. If I have to change actuator body or complete valve and body how does the new one recognize the radio signal from the thermostat. This has probably got a very very simple answer but I have not found any mention of this in the book I am reading.
This is an old house with alterations to alterations. It has 4 CH zones controlled by 6 such 2 port valves.

 

[oilhead]

The valve will be hard wired to a junction box, that is switched by the radio receiver. If you have to change the valve, then if you cannot trace the wires back to the junction box, then you will be able cut the wire and join it following the colour codes.

 

[pete60]

Thanks for that Oilhead. I was beginning to wonder whether that had to be the case. But your post gave me the confidence to get on with the job.
For the benefit of others what I found under the floorboards was, as suspected, a US activator valve. Having loosened and turned it slightly to avoid new pipework that prevented removal of activator body I then clicked off body.
Indicator was at open with manual lever locked in open position. From book / forums I expected duff motor, broken springing or sticky spindle. In fact there were splines broken off the motor spindle and the side was broken off the plastic lever mechanism. (on the replacement this part has been reinforced with extra fining).
I was reluctant to take up extra flooring to get to the junction box, some distance away. So I took a chance and changed the wiring at the valve end rather than the junction box end. I gently prized the body with a small screwdriver to release the micro switch from the old body and clipped it back into the new body. This is the only fixed wiring, the other wires having spade connectors.
Risky maybe, but it worked for me. System working fine now.

 

[oilhead]

I would have 'choc blocked' but well done and thanks for the update.