Mini-split troubleshooting
Symptom-first troubleshooting for when the system is misbehaving but not showing a code. Each page works in order from the checks you can safely do yourself to the point where the job needs a licensed technician, and says clearly where that line is.
If your unit is showing a fault code or a blinking light, start with the error-code section instead — it covers 961 codes across 25 brands and will get you a specific answer faster than working from symptoms.
Two rules worth knowing before you start: never open the refrigerant circuit yourself, and if a system keeps tripping the same protection after a reset, stop resetting it. Repeated resets on a protection fault turn a repair into a replacement.
Your mini split is showing a refrigerant leak code
A2L leak alarms are stop-use events - including one raised by a different room's unit.
Safe checks
Mini split smells bad
Musty, sour or burning smells - what each one points to, and which need the system off now.
Safe checks
Mini split lights blinking
How to read a blinking indicator light, and how to turn a flash pattern into an actual fault code.
Safety callout
Mini split condensate pump problems
A pump that hums, rattles or has stopped - what you can check safely before calling anyone.
Safe checks
Daikin mini split not cooling
Every Daikin code you can act on means something got too hot - and 00 means no fault at all.
Safe checks
Daikin mini split not heating
Defrost, standby and mode conflict pause a Daikin on purpose - plus the heating codes that mean call now.
Safe checks
Fujitsu mini split not heating
A green Economy lamp can mean it is holding the room at 50F on purpose - plus what the blinking lights say.
Safe checks
GREE mini split not heating
E7 means two heads want different modes - plus the GREE codes that are status, not faults.
Safe checks
Mini split indoor unit freezing up
Ice on the indoor coil, which is almost always airflow or refrigerant - how to tell which.
Safety callout
Mini split leaking water
Water dripping from the indoor head - the drain checks you can do yourself, and when to stop.
Safe checks
LG mini split not heating
PREHEAT and DEFROST mean the fan paused on purpose - LG has more normal displays than any brand.
Safe checks
Mini split making loud noise
Rattles, screeches, gurgles and bangs decoded by sound, indoor unit and outdoor unit separately.
Safe checks
Mitsubishi mini split not heating
Mitsubishi U-codes are usually protection trips, not broken parts - and the fix is often airflow.
Safe checks
MRCOOL mini split not cooling
CP means the remote turned it off - plus why all 44 MRCOOL fault codes need a technician.
Safe checks
MRCOOL mini split not heating
Why DF and FP are normal on a MRCOOL, and which codes mean stop using it now.
Safe checks
MRCOOL mini split won't turn on
CP means the remote switched it off - then the power and wiring checks a DIY install needs.
Safety callout
One room won't heat or cool on a multi-zone mini split
One head set to Cool can stop the rest of the house heating - what seven brands call it.
Safe checks
Mini split not cooling
The checks in order, from free fixes to the ones that need a technician and refrigerant tools.
Safety callout
Mini split not heating
Why it blows cold in winter, what defrost looks like, and when it is genuinely a fault.
Safety callout
Mini split outdoor unit not running
When the indoor head runs but the outdoor unit does not - power, control and protection causes.
Safety callout
Pioneer mini split not cooling
The indoor emergency switch can override your remote - plus the codes hiding behind Eco.
Safe checks
Mini split remote not working
Remote troubleshooting from batteries up, including how to run the system without one.
Safety callout
Samsung mini split not heating
C467 means it is too cold outside to heat - and eleven more Samsung displays that are not faults.
Safe checks
Senville mini split not cooling
CP means the remote turned it off, not that it failed - plus the three other displays people misread.
Safe checks
Mini split short cycling
Turning on and off too often - the causes, and why an oversized system is the usual culprit.
Safety callout
Mini split weak airflow
Airflow that has dropped off - the filter and coil checks first, then what needs a pro.
Safe checks
Mini split Wi-Fi not connecting
Getting the app connected and keeping it connected, including the 2.4GHz requirement.
Safe checks