Window air conditioner maintenance checklist
Updated August 2026
A window AC lives or dies by its filter, cleaned or swapped every 2 to 4 weeks during cooling season, backed by a coil wash and perimeter reseal each summer and upright, covered storage over winter. That is the whole routine, all of it DIY. Keep the filter clear and the drain open and a window unit runs its full 8 to 10 years; let it clog and it ices over, molds, and dies at half that.
| Task | Interval | Effort |
|---|---|---|
| Rinse or replace the front filter | 2–4 weeks | 10 min · DIY |
| Wipe the front grille and check airflow | Monthly | 5 min · DIY |
| Task | Interval | Effort |
|---|---|---|
| Wash the evaporator and condenser coils, comb the fins | Seasonal | 30 min · DIY |
| Clear the drain channel and weep hole so water sheds | Seasonal | 10 min · DIY |
| Reseal the perimeter and side accordion panels | Seasonal | 15 min · DIY |
| Straighten bent fins and vacuum the interior | Seasonal | 20 min · DIY |
| Task | Interval | Effort |
|---|---|---|
| Remove the unit or fit a snug exterior cover | Yearly | $15–40 cover |
| Store upright in a dry spot, never on its side | Yearly | DIY |
What neglect costs
A clogged filter starves the coil of airflow, so the evaporator gets too cold, frosts over, and ices into a block that stops cooling and drips water onto the sill. The same trapped moisture breeds mold on the filter and coils, which the fan then blows into the room, a real problem for anyone with allergies. A blocked drain channel overflows inward and can rot the window frame or stain the wall below. The damage is less a repair bill than a wrecked unit: neglect commonly cuts a window AC's 8 to 10 year life down to 4 or 5, and a replacement runs $150–600 by capacity. A rinse every few weeks prevents all of it.
Leave these to a pro
A window AC is built to be owner-maintained, so there is little to hire out. Sealed-system work is the exception: if the unit still ices or barely cools after a clean filter and washed coils, the refrigerant charge is low, and window units are almost never worth recharging, since a tech visit approaches the $150–600 cost of a new one. For a heavy unit going into an upper-story window, paying a handyman $50–100 to install and pull it each season beats a two-person struggle over a ledge. For whole-home options instead, compare the routine with a central AC or the broader HVAC checklist.
This whole checklist ships as reminders in OnOtto: every task above, on the right schedule for your home, snooze-proof.
Load this checklist as remindersFrequently asked questions
How often should I clean a window AC filter?
Every 2 to 4 weeks while the unit runs, more often with pets or heavy use. Most window models use a washable foam or mesh filter behind the front grille: pop it out, rinse it under the tap, let it dry fully, and slide it back. A filter thick with dust cuts airflow, ices the coil, and forces the compressor to work harder for less cold air. It is the highest-payoff task on the unit, and the cleaning page has the full seasonal routine.
Why is my window air conditioner leaking water inside?
Two usual culprits. First, a clogged drain channel or weep hole, so condensation that should shed out the back backs up and spills indoors; clearing it with a wire or compressed air usually fixes it. Second, the unit is tilted the wrong way: a window AC should sit with the outdoor end slightly lower, about a quarter inch, so water drains outside. A frozen coil that melts also floods the pan, which points back to a dirty filter or low refrigerant.
How should I store a window AC over winter?
Either pull it out and store it indoors, or leave it in and cover the exterior. If you remove it, clean the filter and coils, let everything dry to prevent mold, and store it upright in a dry place, never on its side, which can pool oil away from the compressor. If it stays in the window, fit a snug outdoor cover ($15–40) to keep out weather and drafts, and seal the interior side, since a unit left uncovered is a major winter air leak.
Is it worth repairing a window AC or should I replace it?
For most sealed-system problems, replace it. A new window unit runs $150–600 by size, and a refrigerant recharge or compressor repair often costs as much or more, with no guarantee on an 8-year-old unit. Repair makes sense only for cheap, external faults: a dead fan, a bad thermostat knob, or a clogged drain. If the unit is under 5 years old and cools poorly after a full cleaning, it may still be under warranty, so check before you toss it.