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Ductless Mini Split Maintenance & Troubleshooting Tips

Ignoring your ductless mini split HVAC system is easy to do.

After all, it’s virtually silent and needs no input from you once you’ve programmed your smart thermostat.

Unfortunately, even your ductless system needs love and attention from time to time. The Department of Energy’s EnergyStar program offers a partial list of maintenance activities.


Unlike traditional systems, your ductless mini split runs all year long, heating and cooling your air as needed.

Though you don’t need to wake up your system in the early fall and spring as you would a traditional furnace and central air system, we recommend that you keep to a similar maintenance schedule with your ductless system.


The snow, if there was any, is gone and the debris from the last gasps of fall weather now lay uncovered. Issues that have hidden in the cold are now laid bare. 


Go outside and check your condenser and remove all debris from around the unit to keep your vents clear and your unit operating at full capacity.

Trim back foliage that could impede airflow around the unit. If you are planning any new landscaping elements, make sure they are not too close to your condenser or form a wind block that might limit its ability to function.

Air Handlers

Visit each air handler and check their drains. Make certain that there is no standing water or mold growth in the pans. Pour a small amount of water into the pan and make sure it drains steadily.

Once you have proven the drain is functioning properly, add a tablespoon of white vinegar to a ¼ cup of water and slowly pour it into the pan. The vinegar will kill any microorganisms that may be trying to grow and impede the flow in your drain tube.

Check the area around wall and ceiling mounted air handlers for watermarks or softening/swelling of the wall material. These could be signs of a leak inside the wall. Leaks of this sort destroy the structural integrity of your wall.

Air handlers have been known to fall out of walls and ceilings and take half the wall covering down with them.

Replace the filter in each air handler. Filters can fatigue and become less effective over time. While you have the unit open, use canned air to clear out any dust buildup on the blower, coils and anywhere you can see the need.

Use your remote to set your air handler to cool its zone to check its operation before the weather turns warm. Give it enough time to have altered the temperature of the zone before deciding if it is working properly.

Checking to see if the air from the unit feels cold won’t work as your body temp is warmer than the air it uses to heat your home. The air will always feel cool to you. Check your display or use an infrared temperature sensor to observe the efficacy of the air handler’s efforts.

Look at the communication wires running to the control display. You won’t be able to see very much of their length, but you can make sure that the part you can see doesn’t have worn insulation or seem to be stretched tight and under strain.

Your exterior facing walls flex as outside temperatures change and could tug on the lines running through your walls.


Everything you do in the spring you should do in the fall except you should be testing your air handlers for producing heat instead of cooling.

Don’t forget that even their heating function could feel cool on your skin and to rely on the thermostat or your temperature sensor to verify that all is well.


You should clean the filters in your air handler each month. Many are designed to be washable or washable types can be purchased through the manufacturer.

Check the proper operation of your drains every month as well. A backed-up drain can be a devastating problem if it goes unnoticed.

Maintenance Agreements

Many local HVAC service providers offer maintenance plans. These usually include a twice annual inspection and maintenance service for your HVAC system.

We recommend you consider entering in such agreements, especially if your system is new. Many manufacturers require proof of regular professional maintenance before they will honor a warranty repair.

Additionally, a service tech can perform a much more thorough maintenance check of your system including:

  • Drain inspection and clearing
  • Coil cleaning
  • Refrigerant testing – including topping off the supply
  • Inspection and lubrication of internal components
  • System testing with accurate sensor systems
  • Pulling alert data from control modules
  • Checking and tightening mechanical connections/components
  • Leak detection

Troubleshooting Tips

There is little you can do about refrigerant issues without a proper license but there are other problems you can detect and sometimes even solve on your own.

1. Uneven Temperature Between Zones

If one of your zones seems like it isn’t keeping up as well as the others, you need to pay attention. One malfunctioning air handler, if ignored, can take down the entire system.

Make sure the display and your remote are working properly and that there is no error code showing on the display. Make sure the filter is clean and you can hear the blower spinning. If everything looks in order, then you need to call for service right away. If there is an error code, give it to the service company when you call.

2. Noisy Operation

Air handlers should be whisper quiet. If you notice squeaks, rattles or hums coming from an air handler, the blower motor most likely has bearings that are worn.

Call your local HVAC company and tell them the model number of your unit when you request service. Chances are they will be able to bring a new blower unit with them and get you going in a single visit.

3. System Won’t Work at All

If your system won’t respond to any inputs, check your display for an error code. If there is no error code, try going to your breaker panel and toggle the breaker for your system.

Sometimes computer components need to clear out digital noise and a good old-fashioned reboot will solve your problem.

If your system is still unresponsive, you will need to call for service.

4. Poor Performance

If your system operates but isn’t keeping up with demand you could have a refrigerant leak. Other possibilities exist but they all need a professional HVAC technician to solve them.

If you can, without harming the health of an occupant in your home, shut your system down and call for service.

If you allow an under-performing ductless system to keep running, you will cause a snowball effect and damage more components in the system. More damaged components mean higher repair costs.

These are the most common issues you will see in a ductless mini split HVAC system. Just remember that you should never elect to ‘live with’ any performance issues in an appliance, as they will only get worse and more expensive to repair as time goes by.

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