Hi MichealWag,
Congratulations on the new-to-you RV and welcome to the Heartland Owners Forum.
First thing to do is remove the exterior water heater cover on the outside wall of the trailer and see what kind of water heater you have. There's probably a simple twist-retainer that will let you remove the cover without tools.
Heartland has used water heaters made by Atwood and Suburban. If you have a Suburban heater, look under that exterior cover, in the lower left corner, for a small black rocker switch. Usually if the top of the switch is pressed in, it's ON. In addition to the switch inside the coach, Suburban heaters have a secondary switch under the exterior cover. Make sure it's ON.
Other things to check would be the main circuit breaker panel inside the trailer. If not sure which breaker powers the water heater, flip all the breakers OFF and back ON.
Beyond that, if you have a Volt-Ohm meter, use our
Water Heater Troubleshooting Guide to figure out exactly what's wrong. Unfortunately, that guide will only help with Suburban water heaters. Atwood water heater electric operation is very different and is a bit more complicated.