Why would a two port valve stop working?

[garagemc]

Hi,

What would be the most common cause for a two port valve to stop working?

Mine has stopped, but not quite sure why. Could it be the spring? Motor? Limescale?

Is it worth opening up and doing a bit of an investigation? Or should I just get a new one? I have no idea how to fit one, so are there any instructions anywhere?

I will end my barrage of questions now. Thanks for any help.

 

[Homesafe]

Check this out!
http://www.seered.co.uk/index.html

 

[Richard C]

Cos it’s fecked. If you have the skill, by all means strip it down & have a look if youve a mind to but it could be anything from a berggered motor, a blockage or total seizure; I once found a ½ “ strip of swarf embedded in the rubber ball but I could never work out where the hell it came from. In honesty, you have to ask yourself if it’s worth trying to repairing the frigging thing (which could easily fail again in a very short time) or buying a brand new, quality valve off Ebay for probably less than 40 quid & fitting that!
Having looked at the link, not sure what planet newgas is on

 

[muggles]

What's stopped about it, has it stopped moving, has it stopped firing the boiler, or is it permanently open? If it's stopped moving it's either ceased up, the motor's gone, or there's no demand. If it's moving but the boiler isn't firing then it's the microswitch.

To test, with the power off move the lever, if it moves reasonably freely (there will be some resistance from the spring) then it's not ceased. Now set your controls to demand (roomstat up if it's the heating 2-port, cylinder stat up if it's the hot water 2-port, and programmer set to ON). Wait a minute or so, then try the lever again. If it moves more freely than it did before and doesn't spring back, the motor and controls are OK, it's the microswitch that's broken. If it's the same as before and springs back then either the motor has died or there's no demand from the controls, IE a thermostat has broken.

If it's permanently open then the spring may have broken although this is unusual, it may also be an electrical fault (but it would spring back if everything was turned off) or it may be jammed. If it seems to be operating correctly but is letting by then the ball inside is breaking up and you need a new valve.

I think that covers everything. Motors are available separately or you can buy a whole new head, the motor is two wires and a couple of screws, the head is five or six wires and a couple of screws

 

[Richard C]

I think that covers everything. Motors are available separately or you can buy a whole new head, the motor is two wires and a couple of screws, the head is five or six wires and a couple of screws

I think it does & you made a far more thorough job than I did