fourth year
If the bottom element started heating immediately after you turned on the power, then the contacts on the upper thermostat were fused when the element burned out. If you use up all the hot water in the tank so that the upper element should operate, and then tap the thermostat with the handle of a screwdriver, it may unfuse them. Check with the voltmeter again and see if you have 240 volts at the element. If not, change the upper thermostat.
