My mate has asked me to go round his house and see whats wrong with his immersion heater, he said he's changed the thermostat on it but that only lasted a couple of days and now its stopped working again. I haven't done anything with an immersion heater for years and so can't remeber much about them so how do i go about finding out whats wrong with it and also are there any problems which can occur more often than others when deling with an immersion heater?