Ideal s28 water pressure problem

[pipsnell]

Hi
Have hot water but no central heating, turn the thermostat and boiler tries to cut in, suspect it is the water pressure.
Water pressure reading ok at boiler situated in the kitchen. At cylinder on second floor (in airing cupboard) no pressure reading. Have opened the loop to top up but no water flows. Have bleed rads and even let water out, pressure drops at boiler, use loop to fill system but pressure gauge in airing cupboard still does not move.
Ant ideas
Thanks
Pip

 

[kevplumb]

tap it

might well be stuck

 

[pipsnell]

When i tried to top the system up with the loop the pressure gauge in the airing cupboard did not move and no water passed, tried tapping the one way valve (Had already seen you suggest this on another thread)
Bled rads, no air, so let water out which reduced the pressure at the boiler. When i again tried to fill the system water passed through and an increase in pressure was seen at the boiler. However the gauge in the airing cupboard next to the cylinder and loop did not move.
I can not understand this, and have not done anything to the system up until the time I came to try the heating before winter.
Thanks