Squirrels like to nest in the engine compartments of parked vehicles as well as seek a warm refuge inside your RV if they can find access. This is a guide about keeping squirrels out of an RV.
What is a good way to keep squirrels and other pests out of our motorhome that is parked?
By Norma from Bethlehem, GA
Close up all openings. However, if you are talking about the engine compartment there is no way to enclose the bottom of the engine. My suggest is to buy a Havahart live trap from the local hardware store, trap the critters and release them about 10 miles away. You won't get rid of them completely, but you can control the population.
Try Fresh Cab. Works for about 3 months and has no poison. I know it works for rodents I'm not sure if it's labeled for squirrels. Check with the company to make sure.