Honeywell Motorised 3 Way Valve

Hi. Is it possible for a motorised 3 way valve to not be opening and closing correctly even if you can hear the motor operate when required? Every year when I turn the heating right down for the summer and then back up for the winter I seem to have an issue with my condensing boiler and was wondering if the 3 way valve is the cause. The issue (I think) seems to be water flow to the boiler in that after about 15 mins of running from cold, the boiler cuts out even if there is still a demand for it. There is also a lot of noise created around the pump area of the boiler which sounds like the pump operating but not enough water reaching it if that makes sense. After a week or so of this happening things seem to settle down and we are then up and running for the winter/ summer, but then have to go through the same problem in 6 months time. It's becoming a pain. Any suggestions would be gratefully received.
Many thanks. Pete.

it sounds more like air in the pump than a fault with the diverter valve valve.
try bleeding the pump via the the big screw or nut on the face of the pump.
you will get a slight dribble of water but thats normal.

Could you give some more information about your system, for example make/model/type of boiler? Open vented or closed? Any recent maintenance? Chemical inhibitor added or not? How often the rads need venting?

Just got the old crystal ball out....Hmmmm...Softus... slim... dark tee shirt..bald...not quite but shaved.. blond or strawberry blond..(ginger but not as harsh). Nerd type, probably a programmer or something involved in technology...Nothing to do with Plumbing/Heating..

Boiler is a Gloworm Compact 60 (condensing). About 5 years old. Closed system with and automatic bleed valve at the top of the system. Rads very rarely need bleeding. Some have been on and off a few times for decorating but thats about it. What I don't understand is why the problem only seems to occur when the heating side has been shut down for a few months and is then fired up again for the winter? Thanks for your suggestion Superskanker. I'll give it a try.

if you take off thew valve head it could be the spindle sticking just turn it with some grips

Thanks Bob.

Well that's solved that one then. Well done BOB.