In regions where air conditioners see little to no use during colder months, proper storage practices help ensure the unit starts up reliably again once warmer weather returns. Before an extended idle period, running the unit for a short cycle allows any moisture inside the system to be cleared through normal operation rather than sitting inside components over the following months.
Covering the outdoor unit with a breathable cover, rather than an airtight one, protects it from falling debris and dust while still allowing moisture to escape rather than becoming trapped and encouraging rust. Indoor units benefit from a final filter clean before the idle period begins, since a dirty filter left in place for months can allow mold to develop in the humid, stagnant conditions inside a switched-off unit.
Capacitors, which help start the compressor and fan motor, can lose some of their electrical charge holding capacity during long idle periods, so a functional test before the season restarts, rather than assuming the unit will work normally after months of disuse, helps catch this kind of gradual degradation early. Rodents and insects are also drawn to unused outdoor units seeking shelter, so a visual check for nesting material before restarting the unit is a reasonable precaution.