BUZZ is NORMAL. IF it works on LP, then the Tstat and ECO is OK. There is a YELLOW wire on the circuit board connection. When on 120, THAT wire should have 12 volts. IF it does, then you will have to access the rear of the water heater to check the 120 element relay and the element. You do NOT need to OHM an element. NEVER need too. All you do is verify 120 volts at the white and black wires on the element. IF you have 120 volts and NO heat after 2 hours, your element is BAD. They either work or they do not. They do NOT put out a little heat. Doug