Are you watching over the air signals, satellite, park cable, etc. Does it act up if you are watching a DVD?
More specifics are needed.
Interference from a motor most likely would never interfere with a Cell phone. Such a huge difference in the frequency band from that type of noise.
Follow your wires from the fan motor. Clean the ground. Clean your battery posts and all connections. Your battery is the primary source for filtering in vehicles and will also help suppress electrical noise in an RV enviorment.