potterton 50e wot? suprima? profile? if u got a conventional system eg hot water cylinder then chances are its either air above the valve, faulty valve, faulty cylinder stat or possibly programmer u wil need a multimeter 2 prove which 1 is faulty, if u got a combi then u would be looking at flow rate and flow sensor, thernister, diverter valve and microswitch, plate heat exchanger or possibly pcb
blaiross, February 2012