Hi Andy, it is unusual for these models not to give an error so this is a pure calculated guess., Check the drain pump and hose for blockages.Take off the access plate and there should be a stat by the heater with a red reset button. Turn OFF all power and press.If it clicks,you have reset it and all should be okay.If not, could be heater wires or any number of faults so an engineer would be advisable.
FOXY
July 2009