Dirty mini-splits are one of the most common service calls we get, and most of them are preventable. The indoor head has no ductwork in front of it to catch dust, so the filters and coil get dirty faster than a central system. Here is what you can clean yourself and what needs a technician.
Before you start
- Turn the unit off with the remote.
- Switch off the breaker or the disconnect for the unit before touching anything beyond the filters.
- Have a towel ready. Some water may drip.
Cleaning the filters, every few weeks in heavy use
- Lift the front panel of the indoor head. On most models it tilts up and stays open.
- Slide the mesh filters out. They usually pull down and out.
- Vacuum off loose dust, then rinse under lukewarm water from the back side so the dust pushes out the way it came in.
- Use mild soap if they are greasy, for example in a kitchen or near a stove.
- Let them dry completely before putting them back. A damp filter grows mold.
In Sacramento summers, with the system running daily and dust in the air, checking the filters every two to four weeks is reasonable. During wildfire smoke events, check more often.
What you can do on the coil yourself
With the filters out, you can see the front of the indoor coil. If it has a light layer of dust, you can gently vacuum it with a soft brush attachment, brushing in the direction of the fins. Do not press hard. The fins bend easily.
Foaming no-rinse coil cleaners sold for mini-splits exist. If you use one, follow the label, keep it off electrical parts, and make sure the drain is clear so the runoff has somewhere to go.
What needs a technician
The parts that cause most mini-split problems are behind the coil, out of reach without disassembly:
- The blower wheel. The squirrel-cage fan inside the head collects a sticky black buildup. When it is dirty, airflow drops, the unit gets noisy, and it can spit specks of debris. Cleaning it properly means removing covers or using a bagged wash kit and a pump sprayer.
- The drain pan and drain line. Algae and slime build up and cause leaks down the wall. See mini-split leaking water inside.
- A deep coil cleaning when the coil is matted or smells.
- The outdoor unit, including checking electrical connections and refrigerant charge.
Signs a deep clean is overdue
- Musty or dirty sock smell when it starts. See why an AC smells musty.
- Weak airflow even with clean filters
- Black specks blowing out of the louvers
- Water dripping from the head
- Louder than it used to be
- Cooling less than it did last year
The outdoor unit
Keep the area around it clear, rinse the coil gently with a hose with the power off, and keep leaves and debris off the top. No pressure washers.
How often to have it professionally cleaned
For a head that runs most of the year, a professional cleaning of the blower wheel, coil and drain every year or two keeps it running quietly and efficiently. Units in kitchens, dusty garages or homes with pets usually need it more often.
What we do
A mini-split service visit from us covers the filters, coil, blower wheel, drain pan and line, and the outdoor unit, with the refrigerant charge verified. Our diagnostic for problems is a flat $69 and it is credited toward the repair. See how often a heat pump needs service and our ductless mini-split page.
Frequently asked questions
How often should I clean my mini-split filters?
Every two to four weeks during heavy use, and more often with pets, dust or wildfire smoke. Rinse them and let them dry fully before reinstalling.
Can I clean my mini-split myself?
You can clean the filters and lightly vacuum the front of the coil. The blower wheel, drain pan and a deep coil cleaning usually need a technician.
What are the black specks coming out of my mini-split?
Usually buildup from a dirty blower wheel being thrown out by the fan. It needs a professional cleaning.
Why does my mini-split smell musty?
Moisture and dust in the coil, blower wheel or drain pan grow mold and bacteria. A professional cleaning and a clear drain usually fix it.
How often does a mini-split need professional cleaning?
Every year or two for units that run most of the year, more often in kitchens, garages or homes with pets.
Can a dirty mini-split leak water?
Yes. A dirty coil can freeze and overflow when it thaws, and slime in the drain pan or line can block drainage.