[sourdough]

Looks like it is a relatively simple AC circuit. It comes from your switch in the house (when turned on) to the switch on the WH through the thermostat then the heating element....that's it. Turn the switch off at the WH and the one inside on. Make sure the fuse doesn't blow. If it does there is something else on the circuit causing the problem. If nothing happens disconnect feed connection (incoming) to the element (2nd component in line) to isolate the thermostat; turn on the switch at the WH. If it blows then turn off the switch (WH) and disconnect the feed lead to the thermostat (1st component in line). Turn the switch back on; hopefully it doesn't blow and it would indicate the thermostat. Of course what fails, and where, is anyone's guess but that might at least isolate it to something. Good luck.