How easy should a zone valve be to turn?

[bigwold]

I have a Satchwell SM3203 (motor open/motor close) 2 port zone valve controlling the flow to the hot water cylinder which has stopped working. I've removed the actuator and found that when triggering it via the cylinder thermostat it starts to turn but then stops and clicks and won't turn the 90 degrees unaided so assume it need replacing. This is a 30 year old system.

My question is, has the actuator just worn out or has a stiff valve damaged it. The valve was initially hard to turn but now I can turn it with my fingers. How free should it be, i.e. should it spin (obviously not), should I be able to turn it with fingers by just gripping the shaft or, as in my case, is it free enough if I can turn it by spade end?

Thanks for any help

 

[bigwold]

Bump

Can no one really answer this as I don't want to install a new actuator just to have it broken by an over stiff valve?

 

[twgas]

You can normally turn them with your fingers, however once they stiffen up they are on the way out, even if you oil/loosen it. A more worrying problem is they usually go stiff because of dirt in the system.

 

[WDIK]

the gearbox is stripped, replace there is no magic fix