I worked a a RV dealership for several years. I did everything except sell em. Each time we got a trade in it was inspected for expensive repairs. I found several odd things to keep mice away. Owners would take small jars similar to baby food jars and put cotton balls with moth balls or crystals in it and punched holes in the lid. It must have worked because I never saw a trace of one. I saw them placed in the water heater area outside, the fridge area outside, and compartments that you had to access outside. I've never had mice but I've had many ants that were hard to control.:)