In researching RV maintenance issues while waiting for a right class C to come along, I have found that class Cs are notorious for leaks in the cab-over front section, particularly the front window. A couple of forum members also have problems with roof or side leaks in their class A.
I happened to find out about this equipment called Sealtech that RV service centers may have. It pressurizes an RV so that leaks can be found the old-fashioned and reliable way: with soap bubbles. See video. This blower sits inside the RV. It makes so much sense.