This is subject that has been discussed before but one that is worth mentioning again. Some of the newer members may have never thought about it.
Although this specifically addresses roof air conditioners, it is applicable to all bus AC units. In addition to changing/cleaning your filters, you can clean the coils and clear the drain lines.
I assume everyone who has roof airs, has drain lines that drain the condensation under the bus. It is rather important that we watch the drain lines and make sure they are not clogged up. I know one Prevost owner who did not do this, and the damage cost over $8000 for repairs to the ceiling and wall of his coach.
When the drain lines stop up, the result is very similar to what happens in your house. The water has to go somewhere, and when the trough inside the unit gets full, it starts running over. In your house, it usually messes up your carpet, wood or tile. In the bus, the water may run over in your ceiling area. It can do serious damage to ceilings, walls, and floors before you know what is happening. I would recommend checking your drains and flushing with a small amount of detergent and water at least once every couple years.
The last time I did this, mine were working fine, but I still added a few drops of dish detergent and flushed the lines. I was careful not to get any of the detergent on the coils. In my case there was one drain on each side of the AC unit. The 2 lines on each unit "T" into one drain line that goes under the bus. Ray Davis said it was suggested that you blow out the lines from the bottom. That may or may not clear both sides if they are connected the same way mine was, but the theory does make sense. Cleaning of these lines is a rather simple but important maintenance item.
Switch off all power to each unit, and remove the outside cover and the sheet metal cover that encloses the electrical connections. Locate your drain line and mix some water and detergent and see if it flows out the drain. If possible, blow out each line with low pressure air. I did this with a long nozzle on my air line. While you are in the unit, gently blow the dirt and debris from the coils. High pressure may damage the coils. This procedure may prevent serious problems in the future. Always be cautious when walking around on your roof. It is best to use something to walk on and therefore, distribute your weight. Plywood or thick sports pads make a huge difference. At a minimum, put your weight on the joints when you step. Be careful that you don't fall off the bus.
