The recurring ductless repairs are refrigerant leaks at line set connections, condensate drainage problems, sensor and control faults, and indoor coils fouled by neglected cleaning. Most of them trace to installation quality or maintenance rather than equipment defects.

Refrigerant Leaks at the Flares

This is the most common serious failure on ductless mini splits, and it is almost always an installation issue.

Line sets connect to the indoor and outdoor units with flare fittings — a flared copper end compressed against a fitting. Making a good flare requires the right tool, a clean cut, and correct torque. A flare that is slightly off will seal initially and leak slowly over months or years.

The symptom is gradual capacity loss. The unit still runs and still blows cool air, just less of it, and homeowners often live with declining performance for a season before calling.

Refrigerant is not consumed, so a low system has a leak. Adding more without finding it is a delay the compressor pays for, because running low means it operates hot and inadequately lubricated.

Condensate Drainage

Mini splits drain by gravity through a small flexible line, and that line clogs.

The symptom is unmistakable — water running down the wall beneath the indoor head. Because the drain line is small and often runs a long horizontal distance before exiting, algae and dust accumulate readily.

Installation matters here too. A drain line that lacks continuous downward slope, or that was kinked behind the unit, will back up no matter how clean it is. Some installations use a condensate pump, which adds another component that can fail.

Fouled Indoor Coils and Blower Wheels

This is the failure that develops quietly and is entirely preventable.

The indoor coil sits wet whenever the unit is cooling. The blower — a narrow cross-flow drum — collects a film of dust that mixes with that condensation.

Left alone, it becomes biological growth. The first symptom is a musty smell when the unit starts, and it is an indoor air quality problem as much as a performance one. Airflow drops as the wheel loads up, which reduces capacity and can cause the coil to freeze.

Cleaning it properly requires partial disassembly. Washing the removable filters monthly helps but does not reach the coil or the wheel.

Sensor and Control Faults

Mini splits are sensor-dependent, and they self-diagnose. Most faults display as an error code on the indoor unit or through a blink pattern on its LED.

Thermistors drift or fail, causing erratic behaviour — a unit that shuts off prematurely, runs continuously, or reports the wrong room temperature.

Communication faults between indoor and outdoor units are common where the interconnecting cable was undersized, damaged during installation, or run alongside high-voltage wiring.

Write down the error code before power-cycling. Clearing it throws away the most useful diagnostic information available, and intermittent faults are the hardest to catch on a service call.

Outdoor Unit Problems

Capacitors, fan motors, and contactors fail as they do on any system. Inverter boards are the ductless-specific item — they are the electronics that modulate compressor speed, and they are sensitive to power quality and to moisture intrusion in the outdoor cabinet.

In heating mode, defrost cycle problems present as ice building on the outdoor unit that does not clear.

Multi-Zone Complications

Systems with several indoor heads on one outdoor unit have more connections, more line set, and more that can leak.

They can also be sized incorrectly — the outdoor capacity has to cover realistic simultaneous demand, and a system that struggles when every head calls at once is a design problem rather than a fault.

Preventing Most of It

Wash the filters monthly. Have the indoor coil and blower professionally cleaned annually — this single item prevents the majority of the calls above.

Because mini splits heat as well as cool, they run year-round with no off season, which is why twice-yearly service is the honest recommendation. That is covered under our Care Club maintenance plan.

Contact 72 Degrees or call (830) 468-5316.