IF you have a Suburban Water heater the ON/OFF switch for electric is in outside compartment hiding down in left corner behind gas. They have a tendency to fail.
Check switch...replace or open AC circuit breaker
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If you have an Atwood.......OLDER models had electric ON/OFF switch located on backside of WH (inside RV) on the electric junction cover (prior to 2004)
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Which brand/model of WH?
Propane is easy cause you can hear it when flame is lit.
Electric is different as you can't hear it and most don't have any light that indicates on.
SO if water is hot..stays hot then electric is ON