Mini-split check

Does my mini-split need cleaning?

Answer six quick questions about smell, spots, airflow, and water. Get one plain answer: it looks fine, wash the filters first, book a deep clean, or turn it off and call.

Any smell when it runs?

Rotten eggs or gas isn't the mini-split. Leave the house and call the gas company from outside.

No smellMusty, like dirty socks or a wet towelSour like vinegar, fishy, or a chemical smellBurning, hot plastic, or electrical

What do you see on the blower wheel?

Turn the power off at the breaker. Shine a flashlight up through the louvers at the blower wheel, the long round fan inside. If your manual says not to move the louvers by hand, look through them as they sit.

Clean, or a light film of dustSome dark spotsA thick coat, or black flakes blow out

How is the airflow?NormalWeaker than it used to be

Any water coming from the indoor unit?NoDripping or spitting water

When was it last deep cleaned by a professional?Never, or I don't knowMore than 2 years ago1 to 2 years agoLess than a year ago

How much does it run?RarelySummer onlyMost of the year

Answer all six questions, then press the button.

This check needs JavaScript. The table below shows exactly how it decides, so you can read your answer there.

How the check decides

The rules run in order, and the first one that fits your answers decides.

If your answers show	The check says
A burning, hot-plastic, or electrical smell, whatever else is true	Turn it off and call
A sour, vinegar, fishy, or chemical smell, whatever else is true	Turn it off and call
A thick coat on the blower wheel, or black flakes blowing out	Book a deep clean
Some dark spots on the blower wheel	Book a deep clean
Water dripping or spitting, with a clean wheel	Wash the filters first
A musty smell, with a clean wheel	Wash the filters first
Weaker airflow, with a clean wheel	Wash the filters first
None of the above. The last cleaning and how much it runs change the advice on when to look again, not the verdict.	Looks fine, check again when you wash the filters

Method

Your six answers run through the rules below in order, and the first one that fits decides. Burning and vinegar smells always come first. The flashlight look at the blower wheel decides whether a deep clean is due; the last cleaning and how much the unit runs only change when to look again. Every line matches AC Frog's mini-split guides, which cite the manufacturers, PNNL, and EPA.

What this cannot tell you

It can't see inside your unit. A flashlight through the louvers shows part of the blower wheel and little of the coil.
It doesn't diagnose repairs. Ice that keeps coming back, a failed drain pump, refrigerant, and error codes need a technician.
If floodwater reached the unit, don't run it. CDC says to have it checked and cleaned first.
Your unit's manual comes first wherever it says something different.