100% PURE peppermint oil DOES work! Not cheap. But when you figure what it what cost to replace wires it's worth it.
I actually got rid of the hardest of all vermin, gophers, with peppermint oil on cotton balls dropped down all their pesky holes they decided to dig the day after I put my house up for sale.
I had one real determined gopher that just pushed the cotton ball out every day. I fixed him with a wash rag soaked with a whole bottle of peppermint oil shoved down his den.......he moved out the next day! :C
Depending where you stay during the winter with your RV. Spiders like to set up house in RV's down south. I found the natural cure for those is coconut and vinegar in a spray bottle. Drives them right out and your RV smells like you are in Hawaii!