Sounds as though the heater is either wired wrong or blown, it is sometimes the case that if the bearings are really bad the drum cuts through the heater allowing water into short the machine out, this is easy to check by pulling out the heater if OK then check the way you have wired it as from what you say it trips the mains when the machine switches the heater on.
powerhousesteve@hotmail.com
January 2006