Electramate 2000 12 kw

Hi Mike had quick read through other posts to see if there was an answer to my problem but no luck so here goes. The problem is the heating comes on for a short time and then goes off so to get the pump to run again i isolate at the local isolator leave for 30 seconds and switch back on pump runs for a short time the bottom green LED illuminates and pump goes off again. Htg pump head changed a week ago. Also the maim circuit board has only three green LEDs where all the manuals talk about four. thanks in antisipation of a reply.

Sounds like main board.
Check for fault codes and functions.
Mike