Ductless AC Troubleshooting, A Step By Step Guide

With this ductless ac troubleshooting guide, you can find problems with your system, fix it yourself, and save a lot of money. We will guide you through the process of identifying the problem and repairing your air conditioner or heat pump. The normal service charge would cost you over $100 but, with this guide, you can save that money.

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**NOTE** Only you can assess your ability to perform these actions. This is a guide and cannot give the details/procedures for every possible situation.

Is the unit running?

If your unit is not operating, you should begin your ductless ac troubleshooting by checking the display on the fan coil for a fault code. In most units, the display will show an E with a number. With that number you can narrow down the problem by referring to the user manual/installation instructions. Next, you should check the room temperature setting. On most units this is done with the remote control. Ensure that the unit is in the proper mode and the setpoint is correct. You should also make sure the unit has been off for at least three minutes. If the display on the air handler is blank, check the fuse or breaker for the unit. In the case of a tripped breaker, you should check the wiring connections in the outside unit. Some units also have a fuse on the control board in the air handler.

Is it blowing air but not cooling?

Continue your ductless ac troubleshooting by checking the air filter. It should be washed at least every month. Also check to see if there is any ice buildup on the coil. If there is ice build up, check to make sure the fan is working. Make sure the blower wheel is free to move. If it is free and the fan is not working then the problem is probably the motor or the control board. If the fan is working, allow the ice to melt and check the refrigerant level in the unit.

Ductless AC Troubleshooting, At the outdoor unit...

If there is no ice and the fan is working, you should go to the outdoor unit. If the fan on the outside unit is not running, you should check the dual run capacitor. Our capacitor testing guide will help you with that. If the capacitor can is bulging, it is a good indication that it is bad. If the capacitor is good the condenser fan motor may be bad. You can use our fan replacement guide to help you. If the fan is running, feel the compressor to see if it is running. If it is hot to the touch and not running, shut off the power and cool the compressor by pouring water over it. Then, check the outdoor coil and make sure it is clean. You should also check the dual run capacitor. After the unit is running, you should check the refrigerant level. If, after the compressor is cooled down, the unit makes a loud humming noise when it is trying to start, the compressor rotor may be stuck. You can use a hard start capacitor to try to get it to run. If the compressor still does not start, it may need to be replaced. You can use our compressor testing guide to check to be sure. If the fan and compressor are running but the cooling or heating is insufficient, start by cleaning the unit. Ensure the fan coil, filter, and condenser coil are clean. Then you can check the refrigerant level and adjust per the operating instructions.


If the unit's refrigerant charge is adequate, the unit may be improperly sized. The only way to tell if the unit is the proper size is through a process called a load calculation.

Is the unit leaking water?

If your unit is dripping water, you should begin your ductless ac troubleshooting by checking the drain hose to see if it is clogged. The easiest way to do this is with a bottle of water. Outside, stick the end of the hose in a bottle of water. Seal around the bottle opening with your hand. Then squeeze the water bottle and then pull the hose out. The water should drain but this may need to be done a few times to make sure the line is clean. If the hose was not clogged, check to make sure the fan coil unit is sloped properly. The unit should be slightly out of level with the end attached to the drain hose slightly lower than the other end.

Lost or broken remote control?

If the remote does not work, you can replace the batteries. If it still does not work or you can't find it, most units have an emergency button on the fan coil unit that you can push to make it run. It will then operate as necessary to maintain a default temperature. You should complete your ductless ac troubleshooting by observing a complete heating or cooling cycle.