Running? Better description of the sound or vibration would be needed. It could well be the water heater.
When posting problems it is a good idea to mention what model camper you have. Not all are set up the same way.
Chuck - Sparta, TN
2012 Jay Flight 22FB, 2 x Honda EU2000i
2013 GMC Yukon XL Denali AWD
EDUCATION is what you get when you read the fine print.....
EXPERIENCE is what you get when you don't.