Mini Split Not Heating? Settings, Defrost, and Leaks

What you're seeing

• The indoor unit blows cool or room-temperature air in heat mode.
• The indoor fan stops for several minutes, then starts again.
• An error code or blinking light on the indoor unit.
• Oil at a flare connection or frost on one of the service valves.

How to track it down

Work through these in order, or follow along in the video above. Each step rules something out before you spend money on parts.

1. Check the mode and the remote

   Make sure it's in heat, not auto, dry, or fan, and that the set temperature is above room temperature. A remote with weak batteries or the wrong settings is a common cause.

2. Know what defrost looks like

   In heat mode the indoor fan stops while the outdoor unit defrosts. That's normal and can last several minutes. It's also normal for the fan to wait until the coil warms up before blowing.

3. Clean the filters

   The filters on a mini split load up fast. Dirty filters cut heating capacity and can trip high-pressure protection.

4. Read the error code

   Look up the code for your brand and model. It'll point you to a sensor, a communication fault, or a pressure problem.

5. Check the flares

   Mini splits are known for flare leaks, especially when they weren't torqued right. A tech will leak check the flares at both the indoor and outdoor units before adding any refrigerant.

If you're a homeowner

Settings, filters, and error codes are all fair game for a homeowner. If the code points to refrigerant or the unit was recently installed, call a tech. Refrigerant work requires EPA 608 certification.