An important aspect of maintaining your commercial or residential air conditioning systems, along with having them serviced twice a year, is to have the filters changed quarterly (or more depending on the application.) This will help prevent the air filters from getting clogged up which cases the unit(s) to freeze up. This will cause your air conditioning systems to not work! In some cases, filters need to be changed even more often than quarterly. Ask your technician to give you the optimal filter change out schedule.