Central heating problem

[RobbieToo]

I have a central heating problem. The Amptec system switches on for 1 or 2 minutes then switches to alarm. The pipes are hot so I assume it is the pump. Will it matter that the pump is fitted on the bottom of the unit where the cold water goes into the system? And how can I check if the grundfos pump works? Can you feel it on the pump when it runs? And where will the fuse be for a pump? In the pump or more upstream towards the main switches? Or is the assumption above incorrect and can air in the system cause the problem? 

[incitatus]

an airlock in the system can cause this, but it seems more likely that the pump unit needs to be replaced.  check all radiators for air by bleeding them.  the fuse and power supply for pumps are normally located on or near the pumps themselves, but its rarely a fuse, unfortunately.  when a pump runs you can feel the vibration by placing your hand on the pump, though be careful as it may be hot.