Glow Worm Fuel Saver F not working properly ?

If all radiators are getting some heat, probably not pump. Check for air in radiators, bleed valve one end of each radiator, open valve, you will need a key for it, if air comes out, leave open until water comes out. Only do this when cold, keep an eye on water pressure in boiler, should be about 1 bar when cold, if it drops, top up with fill loop on boiler, do that with all radiators, if after that, radiators still not very hot, suspect thermostat in boiler

SD
January 2013