If your home never seems to cool off despite your mini-split running consistently, the system might not actually be cooling. When a mini-split AC isn't cooling but the fan is running, several factors can limit its performance and efficiency, leaving you feeling uncomfortable in your space. Understanding what's happening inside your mini-split air handlers and compressor helps you know when to try basic maintenance or when it’s time to call in a professional for AC repair.
Common Reasons a Split AC Isn’t Cooling but the Fan Is Running
When your mini-split fan is running but you can't feel any cool air, the problem usually involves airflow restrictions, low refrigerant, or electrical issues. Each of these affects how your unit transfers heat between indoor and outdoor components.
Clogged air filter
Air filters trap dust and debris, keeping the components inside each air handler cleaner and maintaining indoor air quality. When a filter is clogged, it restricts airflow and prevents the unit from drawing in and recirculating cool air properly. Restricted air forces your AC to work harder and can strain the evaporator coil, fan, and other components. Replacing air filters regularly prevents undue wear and improves cooling efficiency.
Incorrect thermostat settings
If the mini-split thermostat is set to fan rather than cool, the unit will start the fan rather than actually cooling your space. Similarly, if the temperature setting is higher than the actual room temperature, the compressor won’t engage. Compared to central ACs, ductless mini-split systems may also have multiple heads and zones, each with its own temperature settings, so fixing one thermostat may not address cooling problems throughout your entire home.
Low refrigerant
Refrigerant carries heat from the indoor coil to the outdoor coil, then recirculates to the indoor unit. Low refrigerant reduces the unit's ability to absorb and release heat. If the refrigerant is low, due to either a leak or low charge, your mini split may not cool effectively, even if the fan turns on.
Frozen evaporator coils
Evaporator coils may freeze due to restricted airflow or low refrigerant, which can cause the surface of the coils to become too cold and freeze the surrounding moisture. Ice insulates the coil, preventing it from cooling the air, which results in warm air from the air handler unit even when the system appears to be on. Frozen coils may cause longer running times, overheating, and pooling water from the thawing process.
Why Is Your Split AC Compressor Not Working but the Fan Is Running?
The compressor is located in the outdoor condensing unit of your mini-split system. Connected to one or more mini-split heads, the compressor increases refrigerant pressure and temperature so heat can be expelled outside at the condenser coil. If the compressor is off, the system can't circulate refrigerant and draw heat out of your space during cooling cycles, no matter how fast the indoor fan spins.
Here are a few reasons why your mini-split AC compressor may not be working while the fan is running.
Faulty capacitor
Capacitors provide compressors with an initial burst of energy necessary to start and maintain cooling cycles. A failed capacitor can result in failed compressor starts, humming, or slow, inefficient operation. You may hear the outdoor unit attempt to start and fall silent, while the indoor fan continues to run.
Tripped breaker
Compressors draw significant electrical power. If the compressor's circuit overloads or shorts, it may trip the breaker, disconnecting the compressor from power while the indoor unit's fan remains on.
Overheating
The condenser unit expels the heat extracted from indoors. If debris, such as dirt, leaves, or tree branches, restricts airflow around the condenser, it acts as insulation and prevents the condenser from releasing heat. Modern systems include safety switches that automatically shut down the condenser and compressor when they exceed safe temperatures to prevent damage from overheating.
Operating with low refrigerant also strains the compressor since it causes the system to run for longer periods to compensate for reduced cooling ability. The outdoor unit may also shut down in this case to protect the compressor from permanent damage and failure.
Troubleshooting Steps You Can Try To Fix a Split AC With No Cooling
While some problems require professional attention, there are a few things you can check before calling an HVAC technician for AC repair. These steps help rule out basic fixes for a mini-split that isn't cooling, like incorrect temperatures, and determine whether the issue is serious enough to warrant professional HVAC services.
Warning signs
Before taking action, look for indicators that your mini-split is struggling:
- Airflow from indoor units feels weak or restricted
- The system runs longer than usual
- The unit turns on and off in short cycles
- Frozen evaporator coil or water pooling beneath the air handler
- Hissing or bubbling noises from the indoor or outdoor unit
Troubleshooting steps
If you notice any of the above, take these practical steps:
- Verify thermostat settings: Confirm the system is set to cool and that the temperature setting is below the current room temperature.
- Check airflow: Hold your hand near the air handler to check airflow strength. Weak output may suggest a clogged filter or a damaged fan motor.
- Replace air filter: Inspect the air filter in the air handler unit. If it's dirty, replace it with a compatible filter.
- Examine and clean the outdoor unit: Remove leaves, dirt, or objects blocking airflow around the condenser to enable proper ventilation.
- Listen for unusual sounds: Hissing or bubbling may indicate a refrigerant leak, which requires professional AC repair.
- Check the electrical panel: Look for and reset tripped breakers or blown fuses that may interrupt compressor operation. If the breaker continues to trip, leave it off and call a technician.
If these troubleshooting steps don't resolve your mini-split cooling issues, the system likely requires inspection and repair from a licensed HVAC technician.
Why Professional AC Repair Is the Best Choice
Mini-split systems feature complex electrical, mechanical, and refrigerant-based components. While homeowners can replace filters, adjust settings, and complete basic cleans, most cooling problems require professional repair. Attempting to repair complex components without proper knowledge risks further damage, high repair costs, and personal injury. For instance, the Environmental Protection Agency (EPA) regulates refrigerant handling and requires certification, while replacing a compressor involves advanced electrical knowledge and specialized tools.
Professional AC repair eliminates these risks and restores comfort quickly. Licensed and certified HVAC technicians have the expertise necessary to provide lasting repairs, and they can also provide routine maintenance services to improve the performance, energy efficiency, and operating life of your mini-split system.
Restore Your Mini-Split's Cooling With Ricky Heath
When your mini-split isn't cooling, responding promptly with troubleshooting and professional repair helps restore your comfort. Ricky Heath’s HVAC team offers lasting solutions to keep your system running efficiently through the summer's hottest temperatures. Contact us at Ricky Heath today to schedule professional service.
