Hi I have the above combi installed and have just had to change a radiator in the bathroom, of course I've now lost the pressure in the combi so went to re-pressurize by turning the valve underneath.
Problem is it gives a quarter turn then jumps, spring loaded as though its supposed t do this. Please help
you are turning the prssure relief valve by the sound of things, leave it alone. on your boiler there should be, on the right had underside, 2 small quarter turn taps connected by a small pipe. open them one at a time until the pressure rises. either that or you should have a hose connecting the return and cold water supply pipe.