Siemens 3 port diverter valve

I'm having problems with my central heating and suspect the 3 way valve. The valve is a Siemens MA V322C. The system provides hot water only unless I use the manual override on the valve. I've tested the grey and white wires feeding the valve and these behave as expected depending on the status of the room/tank thermostats and the controller settings. I've removed the motor head in the detachable plastic housing and tested this separately with a 240v supply which seemed to turn the motor okay. I'm starting to suspect the 2 micro switches which are housed in the plastic part of the valve which is attached to the mechanical part.

My question is whether this plastic part of the valve containing the microswitches can be detached from the mechanical part without draining the system? The valve head is pointing towards the back wall of the airing cupboard and so I'm having to work with a small mirror which makes it way more tricky.

Thanks for any help!

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I think the actuator heads on these are removable without draining down, but not on some earlier models! Have a look at the link below, if your head is removable there will be some locking tabs on the side, press them in to remove the head. if in doubt phone siemens for advice!

http://w3.siemens.co.uk/buildingtec...ontrols/documentation/Documents/mav_zav_i.pdf

Thanks TCCHeating. I've already removed the head by pushing in the two plastic retainers on the side. This removes the motor and housing only. Since my original post, I've managed to get to the two microswitches by removing a plastic cover containing the circuitry (diode, microswitches, resistors etc). The microswitches still work fine.

The motor has a resistance of about 2.5 kOhms across the two terminals (is that about right?) and works when supplied with 240V, but for the cost of a new motor (about £15), I'm going to try fitting a new one.

After that, it's a new 3 port valve and I just need to decide whether I'm brave enough to drain the system myself or whether to pay for a plumber to do a proper job!

you have just said that you have removed the actuator so why would you drain it down and fit a complete valve ? the only reason you would replace the valve body is if the mechanical section of the valve was seized or passing ?

Ianmcd, the removable part of the valve contains the motor only. The circuitry remains attached to the mechanical part of the valve so the only way I can see to completely eliminate this as the source of the problem would be to replace the whole valve