When the central heating goes on first thing in the morning by a timer it runs perfectly, however, after about an hour or so later the radiators get cold but the timer is still on. When I check the pump first thing it is very hot and vibrating and the spring loaded leaver below in the Honeywell silver box is forward as I have manually put it there but when the radiators go cold the pump is hot but not vibrating and sometimes the spring leaver is back on itself. Even if I manually put the spring loaded leaver forward again the water still does not go through to the radiators and the pump is still not vibrating but hot.
Any ideas?