I think this generally refers to a fault on the heater relay which controls power to the water heating element. If the relay switch contacts weld or the relay gets stuck, it cannot turn the heater off. The problem is detected by the electronics which detect the water temperature going too high. If you are competent with a voltmeter, this can be confirmed by measuring the voltage at the heater terminals at the back of the drum (Mains voltage !!). It is worth checking the condition of the temperature sensor terminals (also situated on the heater - little plastic plug with 2 wires) to make sure they are not wet or corroded - this can give erroneous temperature readings into the module. If the heater relay is at fault it is usually a module replacement but individual relays can be replaced on the module card with careful desoldering . Good Luck.
Michael, September 2009
