First of all make sure the water heater is filled with water. You will have to drain it to replace the electrical heating element but right now you want it filled with water.
Let's start out with the simple stuff and move on. First, does your trailer have an inside switch to control the electric part of the water heater? If it does, then turn it off, go out side, open the water heater cover and you should see a small black rocker type switch. Turn it off. You might have to remove a pin through the rocker that holes the switch on or off. Once you have that switch in the off position, go back inside. Reset the circuit breaker on the water heater circuit. Turn the inside switch on (if it has one). If the breaker opens, then you have a problem between the circuit breaker and the heater. If it does not, then the problem is at the water heater.
If the circuit breaker did not open, go outside and turn the black rocker switch on. If the circuit breaker opens, then you have a problem at the water heater (most likely). Find a copy of the water heater service manual (usually someone has it online). Go back inside and open the cirucit breaker to the water heater. The best idea would be to unplug shore power while working on the heater. I would check all of the wiring first to see if a bare water is touching the metal some where. Next, using a meter, check the heating element. There are different methods of doing this (check on line). The quick way is to disconnect the element, tape up the connecting wires (safety first) then turn the power back on. If the breaker does not open, then the problem is with the element. Replace it. If the breaker does open, then you more than likely have a problem with the thermostatic device which turns the element off and on. Turn the power off. Since there are numerous models of that water heater, the best is to get the service manual and test the thermostatic device. Make sure that the power is off when you work on electrical parts.
IF you are UNSURE on any of these suggestions, then DO NOT do it. Hire someone who is training and licensed.
Steve & Trudy
Swamplands of Louisiana
Laissez les bons temps rouler!!!!