What should I do if my mini-split is not heating?

What this symptom usually means

A mini-split that runs but does not deliver heat is a heat-transfer problem, not just an airflow complaint. The indoor head can still move air even when the refrigerant circuit is not bringing enough heat inside, when the system is stuck in defrost, or when a multi-zone control conflict is preventing that room from getting the heat call it needs.

What to look for before service

If airflow feels normal but the air never becomes clearly warm after 10 to 15 minutes in HEAT mode, a refrigerant, reversing-valve, or control issue moves higher on the list. If airflow is weak and the room stays cold, one indoor head may have a fan, sensor, or board problem that limits heat output. If you see ice on the outdoor unit or refrigerant lines, or you notice water after the unit tries to heat, defrost trouble or low refrigerant becomes more likely. If only one room or zone will not heat, the issue is often specific to that head, its sensor, or the way the zones are calling for operation.

Why this page is different from cooling or freezing problems

Heating failures on mini-splits have a few clues that do not fit other symptoms. The unit may blow room-temperature air instead of no air, it may pause indoor airflow briefly during defrost and then resume, and one zone can lose heat because another zone is commanding a different mode. That pattern is different from a dedicated no-cooling complaint, a clear leak complaint, or a page focused mainly on noise or visible icing.

What a technician usually checks

On a service visit, the technician typically verifies operating mode and zone calls first, then measures supply-air temperature rise, checks thermistors and control codes, and inspects whether the outdoor unit is entering and leaving defrost correctly. If those basics do not explain the problem, they test refrigerant pressures and temperatures, inspect for leak signs, and confirm whether the reversing valve is energizing and actually shifting into heating.

What affects repair cost

Lower-cost fixes are usually control-related, such as correcting settings, replacing a handheld remote, resetting addressing on a zone, or changing a thermistor, often in the rough range of $150 to $500 including diagnosis in many markets. Mid-range repairs can include an indoor fan motor or control board, often around $350 to $1,200 depending on brand and access. Higher-cost heating failures usually involve refrigerant leak testing and sealed-system work, reversing-valve repairs, or major board problems, which commonly land from about $900 to $2,500 or more, especially on multi-zone systems where labor and refrigerant quantity are higher.