We have been camping a few times this winter... Running mainly the furnace as well as the heat strip in the A/C unit. However, on a couple of days, we needed to run the A/C during the middle of the day to cool off the camper. When doing so, the camper would always smell musty. I have cleaned everything on the inside of the A/C, but it still smells. Is there anything on the outside unit that needs to be cleaned?? Also, Is there any maintenance that needs to be done on the outside unit??