I have had to replace the motor on a 2-port sunvic type valve in my CH system. I believe the reason for the motor failing is because the valve is very stiff (cannot turn it by hand, I need to use pliers).
So a couple of questions: is it possible to get a valve stem replacement, or is it necessary to buy the whole thing? I'd like to avoid draining half my system to effect this repair/replacement. Has anyone used those small freezing kits (as sold by Screwfix for about 9 quid) on pretty big pipes (about 28mm)? Anyone got any better suggestions?