A mixture of sugar and boric acid(easily bought at any pharmacy) dissolved in hot water, and then put in little cups or bottle caps around the areas of the coach that has a problem. This will kill all of the ants and they will carry it back to the queen to kill the entire colony.
Since we keep the small bait cups in our coach, we do not have a problem with ants at all. This works for the black, red, and fire ants.
This also kills other insects but since you are asking about ants.......