You don't mention what trailer you've got, but, I'll take the guess that it is one of the versions with the kitchen, at least the refrigerator in a slide. Most non-slide refrigerators have a roof vent that acts like a siphon and don't have fans...
Could be any number of reasons why it would be running. Usually they are thermistor controlled; i.e., the temperature behind the refrigerator controls whether the fan runs or not. The fan aids in pushing the accumulated heat out a sidewall mounted vent (they aren't as efficient as a roof vent). Some are on a timer, but, I've only seen those on "high end" RVs, but, those, still, only run when the refrigerator's LP burner is lit. If CruiserRV used the Dometic optional fan assembly, then it is thermostat controlled and you may have a faulty thermostat.
One thing you should verify is that the refrigerator itself isn't running almost full bore...if the refrigerator's burner is lit, the fan should run to get rid of the heat buildup and if your refrigerator is lighting frequently, the fan will cycle like that to keep it cool. If your refrigerator isn't cycling rapidly (burner lights, runs a while, cuts off, but, lights again in a few minutes) then you'll have to troubleshoot that particular refrigerator. Different models have different control mechanisms. You can get your model number off a plate on the refrigerator and then go to the Dometic site (Dometic Manuals
) and look for your model number. They also have installation instructions on the site along with part numbers to give you a better idea of what you are looking at.
Sorry, can't be of any more help than that without actually seeing your installation.
(BTW...whenever you have a question about your rig, it always helps to give the year and model of the trailer if that information isn't in your signature; CruiserRV makes a boat load of fine RVs and some are quite different in layout and design which makes a difference in how they are built and outfitted