How to Fix These 6 Common Window AC Problems

Stephanie Shaykin
Updated August 6, 2021
Professional repairing window air conditioner from outside
Andrey Popov -

If your window AC unit is on the fritz, it could mean a simple fix or a call to a technician

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Air conditioning units can be a lifesaver during the scorching summer months, but they are not without their problems. Find out how to fix some of the most common window air conditioning problems—or learn what to say when you call a pro for help—so that you and your family can stay cool all summer long.

Window AC Troubleshooting: Parts To Inspect

Familiarizing yourself with the individual components of your air conditioner is the unofficial first step. Finding out which part isn't working will allow you to identify and repair any problems quickly or give your pro the knowledge to help you more easily.

  • Face panel: Removing the grille cover, also known as the face panel, that often sits in front of your air conditioner is always a priority. Depending on the unit you have, it may use only screws or clips, or tabs to keep it in place.

  • Filter: The filter protects the air conditioner's internal components from dirt and debris. It also cleans the air before recirculating it back into the room. The filter might be inside or behind the face panel. 

  • Evaporator: The evaporator converts hot air into cool air. The copper tubing houses refrigerant, which helps to complete this process. The coil contains the refrigerant that will cool your room, and it's surrounded by thin aluminum fins to increase efficiency.  

  • Condenser: The condenser is the part of the window air conditioner on the back of the unit that moves the hot air out of your home.

  • Refrigerant: A liquid circulates through the air conditioning unit's evaporator and condenser coils to produce cool air. You should not attempt to handle this substance. 

  • Compressor: The compressor turns the liquid-state refrigerant into a hot gas. The evaporator cools it down at the same time to return it to its original state. 

  • Thermostat: The thermostat is a copper tube sensor. It regulates the air conditioner's on/off cycle and usually clips onto the front of the evaporator.

  • Drain pan: The angled pan at the bottom of the unit collects moisture produced from the evaporator and prevents moisture from leaking into your room. The pan directs it towards its drain port on the back of the frame. 

  • Condensation drain: The condensation drainage system connects the overflow pan to the drainpipe.

  • Sensor wire: The sensor wire on a window air unit is located in front of the evaporator on the AC. This wire turns the unit on and off based on the temperature in the room’s air. 

Safety Protocols for Window Air Conditioning Units

To ensure safety, you should disconnect your air conditioner from power before checking for the source of a problem. Do this by taking off the cord at the wall or switching the breaker that operates it. Make sure you're following the manufacturer's guidance when troubleshooting. 

While you can attempt to look into some small problems by cleaning your unit and clearing obstructions, you should always contact a repair technician to perform any electrical work.

1. AC Unit Won't Turn On

If your window AC doesn’t turn on, check if it's receiving power. Unplug it, then plug a different appliance into the same outlet. If it still doesn't turn on, check your circuit breaker. 

If the AC has power, the problem could be related to a number of components within the unit, including the wiring, thermostat, compressor, selector switch, or control board. These items should be repaired by a local window AC repair technician.

2. Pressure Charge or Refrigerant Leaks

If your air conditioner has low refrigerant, either the pressure in the system was not charged enough or leaks are present. Either fix should be done by a professional. 

The most common leaks are in the tubing on top of the unit (evaporator), at connections to coils and fittings (condenser), or from its drain pan. The types of leaks that will be present depend largely upon where they started. For instance, if there's an evaporator leak, frost may form inside the piping, leading to more noticeable dripping near the outside unit.

A local window AC repair technician will diagnose any problems with the unit and, if there is a leak, fix it before releasing the unit. Then they will charge the system with refrigerant before testing it.

Window air conditioner outside of apartment
James -

3. You Don’t Perform Routine Maintenance

Maintaining your air conditioner is the best way to avoid having to fix it in the first place. Dirty filters and coils cause AC units to work less efficiently. The filter is the leading cause of it failing prematurely.

To keep your window AC running smoothly, maintain it properly. Maintenance can protect you from being stuck with a busted unit during the hot summer months.

To prepare for air conditioning and maintain it during warmer months, take the following steps:

4. The AC Unit Turns On and Off

If you’ve already performed the troubleshooting in step one, this is another one that you won’t be able to tackle yourself. Your AC unit could be plagued by one of a few things, but you’ll probably need to call in a pro to narrow it down.

A professional AC repair person will service and check for electrical connections and contacts for corrosion. Worn-out compressor and fan controls will often produce the same effect when units turn on and off rapidly.

5. AC Unit Isn’t Cooling Properly

Room air conditioners have sensors that measure how cold the room is and control the flow of coolant. If these sensors break, your air conditioner might constantly cycle or won’t change to the proper temperature.

The sensor wire should bend so that it's near the coil but not touching it. You can easily do this yourself, so it senses the temperature correctly but be sure the unit is turned off and that you’re using caution.

You can also check the air damper. If it's open, it will bring in outside air, which is bad for efficiency. Also, check the back cover, which many people forget to remove after the winter season. Finally, check the condensing coils, which are located on the warm end of the air conditioner. Remove the air conditioner's cover to access the coils, and clean them with a soft brush.

6. Drainage Obstruction Caused a Leak

Condensation drainage obstruction is the number one cause of a window air conditioner leaking outside the house. Dirt and debris buildup could interfere with the airflow and cause condensation buildup. 

To fix these problems, check the condensation drain to make sure it is working correctly with no obstructions and it's mounted on a surface that won't slope away from the drain.

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