Short answer: The most common signs are a musty or dirty-sock smell, black spots on the vanes or blower wheel, weaker airflow, water dripping from the head, and a room that won’t heat or cool like it used to. If you see any of these, the inside of the head likely needs a deep clean, not just a filter rinse.
The 6 most common signs
- A musty, sour or dirty-sock smell when the head turns on. That’s usually mold or bacteria growing on the damp coil or blower wheel. See why your mini split smells.
- Black or gray spots on the vanes, or on the blower wheel you can see behind them.
- Weaker airflow even after you’ve rinsed the filters.
- Water dripping or spitting from the head. Carrier lists a dirty coil and a clogged drain line among the common causes.
- The room won’t heat or cool like it used to, or the unit runs constantly to keep up.
- Dust blowing out when the head starts, or dust caked on the front of the coil.
How to check your mini split yourself
Turn the head off at the remote. Lift the front cover and pull out the filters. Look at the coil behind them with a flashlight, then look up through the vanes at the blower wheel. A clean wheel is the color of the plastic. A dirty one has dark, fuzzy lines along each blade. If the wheel is dark or the coil is matted with dust, it’s time for a professional cleaning.
Signs that point to something other than dirt
Not every problem is a cleaning problem. A vinegar, sharp or burning smell can mean an electrical part is overheating; Trane recommends shutting the unit off and calling for service. Ice on the indoor coil, error codes and loud grinding noises usually need an HVAC technician. We clean mini splits; we don’t repair them, and we’ll tell you if we see something that needs a technician.
What a professional cleaning fixes
We open up each head and clean the coil, blower wheel, filters and housing with coil detergent and a rinse setup that catches the runoff. That clears the buildup behind most smells, weak airflow and dust. With us, the first indoor head is $289, and the price per head goes down the more heads we clean in one visit.
Frequently asked questions
How do I know if my mini split is dirty?
Look up through the vanes at the blower wheel with a flashlight. Dark, fuzzy lines on the blades, a dusty coil, a musty smell or weak airflow all mean it needs cleaning.
Why is my mini split blowing less air?
The most common causes are dirty filters, a dust-matted coil or a dirty blower wheel. If rinsing the filters doesn’t help, the inside of the head needs a deep clean.
Why is my mini split dripping water?
A clogged drain line or pan, a dirty coil or a head that isn’t level are the common causes. A cleaning clears the first two.
Are black spots on my mini split mold?
Usually, yes. Black spots on the vanes or blower wheel are most often mold or other growth. See our guide to mold in mini splits.
Related guides
- How often to clean a mini split
- Why your mini split smells
- Mold in your mini split
- Cleaning a mini split yourself vs. hiring a pro
- How much mini split cleaning costs in Vermont
- Dryer vent cleaning
Sources
- Carrier: Why is my mini split leaking water?
- Trane: Why does my mini split smell?
- Energy Vanguard: Ductless mini splits can get nasty inside
- U.S. Department of Energy: Operating and maintaining your heat pump
Book a mini split deep clean
Mansfield Services cleans mini splits across Chittenden, Lamoille and Franklin counties. Book online in a couple of minutes, or call or text (802) 777-3210.
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