Electric Hot water heater was working. Turned well pump off and went on vacation for three weeks. Got back and found I had no hot water. Call Whirlpool, their heater, they told me to replace both upper and lower thermostats after I gave them some voltage and resistive measurements. Replaced thermostats and still doesn't heat water. Measured the voltage across pins 1 and 3, the input of the upper thermostat, and got zero volts. However, I get 120 volts from pin 1 to ground or 120 volts from pin 3 to ground. Shouldn't I be getting 240 volts across pins 1 and 3? Please help. By the way, I get 12.5 ohms across each element.

Yes, you should have 240V between 1 and 3. Reset circuit breaker. First guess is that one leg of double breaker has tripped. The 120v from terminal 3 would be back circuit through heating element. Check electrical connections at breaker and at connection to heater.

Thanks,
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