When a mini split or heat pump misbehaves, mini split troubleshooting usually comes down to a handful of common causes: restricted airflow, a clogged condensate drain, wrong settings, a tripped breaker, low refrigerant, or a communication fault between the indoor and outdoor units. Many of these have safe, homeowner-level fixes — and the symptom itself (not cooling, leaking, freezing up, won’t turn on) tells you where to look first. This guide walks through each symptom, the likely causes in order of probability, and exactly what’s safe to check yourself before calling a licensed pro. If your unit is showing an error code instead of just a symptom, start with our error-code guides to decode it.
First checks for almost any problem
Before diving into a specific symptom, run these safe, five-minute checks:
- Settings: confirm the remote is in the right mode (Cool/Heat) and the set temperature actually calls for it.
- Power: check the breaker and any disconnect at the outdoor unit; try one full power cycle (off at the breaker ~1 minute, then on).
- Filters: pop open the indoor unit and clean or replace the air filters — a dirty filter causes a surprising number of “not cooling,” “freezing,” and “weak airflow” complaints.
- Airflow: clear leaves, snow, and debris from around the outdoor unit and make sure nothing blocks the indoor unit’s intake or outlet.
- Drain: if you see water indoors, check the condensate drain line for clogs.
If a problem remains after these checks — or you see ice on the lines, hear the compressor struggling, or get a repeating error code — it’s time for a closer look (or a pro).
Troubleshoot by symptom
Detailed step-by-step guides for each common symptom are rolling out below. In the meantime, if your system shows a fault code, the brand error-code guides will tell you what it means and whether it’s safe to address yourself.