Replacing a motorised valve

[gbb]

Try the manual overide lever on the end of the housing first. If you can't turn the valve manually it is probably the valve sticking. If you can operate the valve manually, then most likely the motor is fubar.

Yep, my last two failures have been the spindle sticking. Remove motor, Remove circlip on the spindle, apply some light oil to the spindle/ valve interface, work spindle while making sure you don't pull it . Once free, refit circling. Not actually sure if it's neccessary to remove it tbf but I always do .
edited to add, this is the valve itself, the spindle sticks with corrosion I guess.

 

[rogerzilla]

Similarly, circulating pumps can jam, whether separate or inside a combi casing. Coin to remove the access cap, then get a big screwdriver and work the spindle until the piece of scale or grit is crushed or pushed aside. It can then go years without jamming again.