6 possible causes of a window air conditioner not cooling enough

As the summer heat starts to set in, there’s nothing more frustrating than a window air conditioner that just isn’t doing its job. If your AC unit is running but not providing the cool air you expect, it can make your home feel stifling and uncomfortable. Fortunately, there are several common issues that can cause a window AC to underperform, and many of them are relatively easy to diagnose and fix. We’re here to help you get your unit back in top shape so you can enjoy a refreshingly cool space all summer long.

If you find out that you need any replacement parts for your appliance while you’re troubleshooting, you can enter your model number at AppliancePartsPros.com to order them. Most orders arrive in just two business days, and we have thousands of free guides to show you how to install your new parts.

The part replacement information provided in this article may not apply to your specific appliance model. While we strive to offer helpful advice for DIY appliance repairs, variations in models and configurations can lead to differences in troubleshooting steps, error codes and part replacements. For the most accurate guidance, we strongly recommend consulting the technical sheet for your specific appliance model.

Safety precautions

When working on any appliance, remember to keep safety first. Here are some tips to keep in mind: 

• Always power off and unplug your appliance or switch off the circuit breaker before attempting any maintenance or replacement work. This keeps you safe by preventing any risk of injury from electric shock.
• Wear insulated work gloves to protect your hands from sharp metal parts, pinching hazards and debris.
• Take your time and don’t rush while working to prevent accidents and personal injuries.
• Work in a well-lit area so you can clearly see and access the interior parts.
• Clear your workspace of clutter and other obstacles. Keep children and pets away from the work area.
• Never work on internal parts with bare wet hands. Make sure the work area is completely dry.
• Check your user manual to see if there are specific installation or safety instructions for your part or appliance. 
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause injury.
• Wear safety glasses when working with chemicals, dust or cleaning large debris to prevent injury. 
• If the appliance has recently been used, give it plenty of time for any heating parts to cool down before working on it. 
• Take pictures or make a note of wiring terminals or other connections before disconnecting to prevent any problems with reassembly.
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.

Troubleshooting steps

1. BTU inadequate for room:

1. If the BTU rating is too low for the room size, the unit will struggle to cool the space effectively. 
2. In this case, you’ll need to replace the window AC with a larger, more powerful unit that is properly sized for the room.
3. Check the BTU rating of your air conditioner unit.
4. Measure the square footage of the room the AC unit is installed in.
5. Compare the BTU rating to the recommended BTU output for the room size.
6. As a general guideline, you need around 20 BTU per square foot of room space.

2. Filter clogged:

1. A clogged filter restricts airflow, preventing the unit from circulating and cooling the air effectively.
2. Remove the air filter from the window AC unit.
3. Examine the filter – if it is dirty, clogged with dust and debris, it needs to be cleaned or replaced.
4. Clean the filter by rinsing it under running water or using a vacuum hose. If the filter is damaged, replace it with a new one.

3. Outdoor air leaking into room:

1. Properly sealing the unit in the window is crucial to maintain the cooling effect and prevent hot outdoor air from entering the room.
2. Inspect the seal between the air conditioner and the window frame.
3. Look for any gaps or cracks where outdoor air may be entering the room.
4. Replace the accordion side panels and any foam/rubber seals if they are worn or damaged.

4. Fan bound or broken:

1. A properly functioning fan is essential to circulate the cooled air throughout the room.
2. Examine the fan blades inside the unit – check if they are spinning freely without any obstruction.
3. If the fan blades are stuck or damaged, you’ll need to replace the fan blade assembly.
4. Examine the fan motor as well – if it is faulty, the motor will need to be replaced.

5. Thermostat faulty:

1. A faulty thermostat cannot accurately regulate the cooling output.
2. Use a multimeter to check the continuity or resistance of the thermostat.
3. Compare the readings to the technical specification sheet for the correct resistance values.
4. If the thermostat is not functioning properly, it will need to be replaced.

6. Refrigerant leaking from unit:

1. If the unit is low on refrigerant, it will not be able to effectively cool the air.
2. Refrigerant leaks require the expertise of a certified HVAC technician, as they have the proper equipment and knowledge to handle refrigerants.
3. Do not attempt to refill the refrigerant yourself, as this is regulated and requires special training.
4. The technician will need to locate and repair the leak, then refill the refrigerant to the proper level.

Additional information

Thank you for reading! We hope this guide helped you get your window air conditioner working again.

If you have any other appliance repair needs or projects, don’t hesitate to explore our other troubleshooting guides and videos. 

If you need replacement parts or some extra help with ordering them, grab your model number and head over to AppliancePartsPros.com, where you can chat with a pro, read our DIY blog and more.

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Keep Reading: 

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