Gary......yes and no. The Diplomat came with a 12 volt heater in the wet bay. It uses a snap disc to turn the heater on at a certain temperature (I forget the number now). That's the good news. The bad news is that many of the 12 volt heaters never worked when needed.
You can test yours. The snap disc looks like a small flat camera battery, about a dime in size and is located within a few inches of the heater in your wet bay. Inside your coach, at your control panel that has your inverter control, tank gauges, etc, there is a switch that says "System Heat" with a light next to it. Turn this switch on. The light will not come on until the snap disc turns on the heater. With the switch on, go outside and place an ice cube against the snap disc. If the heater works, it will come on.
If you're going to have hook ups, it's probably easier to throw a small heater in the bay or a couple of 100 watt trouble lights.
Don & Mary
2014 Newmar Dutch Star - All Electric - 450 ISL
2016 GMC Canyon 4WD Crew Cab