What's on a mini-split maintenance checklist?
Updated August 2026
Ductless upkeep is mostly a filter you rinse every 2 to 4 weeks, plus a yearly deep-clean of the blower wheel and coil to stop mold, a clear condensate line, and one pro service a year. The blower deep-clean is the task people skip and then regret: a musty smell from the head is the top mini-split complaint, and it is mold growing on the wheel. Keep up with it and a ductless system lasts its 15 to 20 years.
| Task | Interval | Effort |
|---|---|---|
| Pop the front cover and rinse the mesh filters | 2–4 weeks | 10 min · DIY |
| Wipe down the indoor unit housing | Monthly | 5 min · DIY |
| Task | Interval | Effort |
|---|---|---|
| Check the condensate drain line runs freely | Quarterly | 10 min · DIY |
| Wipe visible mold off the vanes and fan outlet | As needed | 10 min · DIY |
| Task | Interval | Effort |
|---|---|---|
| Deep-clean the blower wheel and evaporator coil | Yearly | $150–300 pro or DIY kit |
| Clean the outdoor condenser coil | Yearly | 30 min · DIY |
| Task | Interval | Effort |
|---|---|---|
| Check refrigerant, drain, and line-set | Yearly | $120–250 pro |
What neglect costs
The filters are easy, so the failure mode is almost always the parts you cannot see. Skip the yearly deep-clean and mold colonizes the blower wheel and coil, blowing spores and a sour smell into the room; a professional blower-wheel cleaning to fix it runs $150–400. A neglected condensate line clogs with algae and drips down the wall, staining drywall. Dirty coils also cut capacity, so the head runs longer and your bill climbs. None of it is expensive to prevent, only to ignore.
Leave these to a pro
Once a year, have a tech do a full service ($120–250): they check the refrigerant charge and line-set, clear the drain, and can do a chemical-pressure wash of the coil and blower that goes further than a wipe-down. The annual deep-clean is the one worth paying for if you are not comfortable pulling the cover and bagging the unit, since it is fiddly and easy to soak the control board. Rinsing filters and keeping the outdoor unit clear stay firmly in the DIY column.
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
Why does my mini-split smell musty?
That sour, dirty-sock odor is mold and mildew growing on the always-damp evaporator coil and blower wheel inside the head. Rinsing the filters helps but does not reach the wheel, which is why the smell keeps coming back until you deep-clean it. Running the unit in fan-only mode for a few minutes after cooling dries the coil and slows regrowth. If the smell is strong, book a professional blower-wheel cleaning.
How do I clean mini-split filters?
Open the front panel, lift out the two mesh filters, and rinse them under lukewarm water (no hot water, which can warp them), then let them dry fully before reinstalling. Do it every 2 to 4 weeks in heavy-use season. They are reusable, so you rarely buy replacements. While the cover is open, check the small optional filters some models add and vacuum dust off the intake grille.
Can I deep-clean a mini-split myself?
Yes, with a mini-split bib kit (a $20 to $40 wall bag that funnels runoff into a bucket) and a pump sprayer of coil cleaner. Power off first, bag the unit, protect the control board, and rinse the coil and blower until the runoff clears. It is a couple of hours the first time. Many owners still hire it out yearly because soaking the electronics is an easy and costly mistake.