What type of central heating do I have?

Sounds like you have a bog standard CH & indirect HW system. Assumming its not always been like this, then its most likely the 3-way valve. It may be moving but the ball inside may not be sealing the CH port. In this case try taking off the actuator head and operating the shaft by hand. If its not moving then the small electric motor in the actuator head that drives it is probably knackered - they are easy to get hold (even at B&Q) of as they seem to often go esp. on 3-way valves. These are a lot easier to change than draining down the whole system to change the valve body.

Sounds like a bog standard fully pumped system. Sounds like your valve isn't working though. How are you sure that the actuator is moving OK? Are you sure that the actuator is turning the valve all the way?

Rich

Had the actuator in my hand while wife turned heating on and off. Seemed to be moving all the way. The little over-ride switch seemed to be moving through the full range.

Sounds like you have had the actuator head off so does the shaft of the valve itself turn easily? Note the movement is not much.

"O.B." wrote in news:1122020726.259160.212570 @z14g2000cwz.googlegroups.com:

Around 5-10 degrees. If you have the pump running then turn the valve shaft clockwise with a pair of pliers you should hear the water flow change as you shut off the radiator loop. This clockwise action is usually effected by the spring in the actuator with the synchronous motor winding it anticlockwise (from above) when the room stat is on.

Check the actuator; with the heating off the lever should rest in the middle and you should be able to wind it open by pushing the lever. The motor should then wind anticlock when the radiators are required ie. the CH is on on the programmer and the temperature is lower than that set on the room stat.

It is possible that the actuator want't sitting on the valve shaft properly, too. Make sure it goes right down when you fit it back on; you will have to push and the mechanism completely open as you fit it to be able to get the screws to line up.

The shaft does turn easily with pliers, as you say not much.

Can't hear the flow changing when valve is operated. Actuator seems to be sitting correctly.

Inside these things its usually a hard rubber ball on a small arm. The ball covers either port or leaves both open when its in the middle. If the pump is running when you move the shaft from one side to the other you really ought to hear the water change direction. Perhaps the ball is persished or the ports are gunged up with scale, so the ball can't stop the water flow. The only real way to find out is to drain the system to below the valve and take the top off the valve body itself.