5 common window AC problems and how to fix them

Window air conditioners are a popular choice for many homeowners and renters due to their affordability, efficiency, and ease of installation. They provide a convenient way to maintain individual rooms or small living spaces, especially during hot summer months. But, like any appliance, they can sometimes develop issues that require troubleshooting and repair.

Let’s walk through some of the most common issues that can affect window air conditioners. By identifying and addressing any problems early on, you can keep your unit running well and enjoy a comfortable indoor environment any time of the year.

If you find out that you need any replacement parts for your air conditioner 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.

Disclaimer: The troubleshooting information provided in this article is based on general service manuals and 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 you attempt any maintenance or replacement work. This keeps you safe by preventing any risk of electric shock.
• If the appliance has recently been used, give it plenty of time to cool down before working on it.
• Take your time while working to prevent accidents and personal injuries. Rushing is the enemy of precision.
• Work in a well-lit area so you can clearly see and access appliance parts.
• Keep your workspace free of clutter and other obstacles. Keep children and pets away from the work area.
• Check the user manual to see if there are specific installation or safety instructions related to your appliance or replacement part.
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause personal injury.
• Wear insulated work gloves to protect your hands from sharp metal parts and debris.
• 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.
• Don’t test live voltage with a multimeter if you’re unfamiliar with how to prevent short-circuiting.
• Consider wearing safety glasses and/or a dust mask when working with chemicals, dust or a large amount of debris to prevent irritation or injury.

Read more: Choosing An Air Conditioner: How Many BTUs Do I Need?

Common window air conditioner problems & solutions

Here are some of the most common issues that can show up in window AC units and how you can fix them without the need for an expensive service call:

1. The AC isn’t cooling enough

If your window air conditioner isn’t cooling the room enough or the airflow feels weak:

Check the surroundings

1. Look over the unit to make sure it’s installed correctly. It should have the right tilt angle for drainage and be securely mounted in the window.
2. Check the window seals and insulation around the unit for any gaps or air leaks. If you find any damage or gaps, replace the appropriate part.

Check and clean the air filter

1. Remove the front panel of the unit.
2. Inspect the air filter for dust and debris buildup. If the filter is dirty, vacuum it or wash it with warm soapy water. Allow the filter to dry before reinstalling it.

Replace the filter if it’s damaged or worn out.

Inspect and clean the evaporator and condenser coils

1. Find the evaporator and condenser coils in your unit. They may be accessible from the front, side, or back of the air conditioner.
2. Gently vacuum the coils with a brush attachment to remove dust and debris.
3. If the coils are heavily soiled, use a coil cleaner according to the manufacturer’s instructions. Rinse the coils with water if needed and let them dry completely before reassembling the unit.

Adjust the thermostat settings

1. Make sure the thermostat is set to an appropriate temperature for cooling. You should keep an AC set to 72-76° for comfort and a lower energy bill.
2. Test the thermostat by adjusting the temperature and monitoring the unit’s response. If the thermostat isn’t functioning properly or seems unresponsive, you may need to replace it.

IMPORTANT: If the above steps don’t resolve the issue or if you suspect a more complex problem, such as a refrigerant leak or a malfunctioning compressor, contact a professional HVAC technician for assistance.

2. The unit is making excessive or unusual noise

If you hear rattling, buzzing or grinding sounds coming from your window AC:

Check for any loose parts

1. Remove the front panel and any additional covers to access the internal parts.
2. Check the interior for any loose parts such as screws, bolts, or brackets. Tighten them as needed.
3. Make sure the fan assembly is secure and correctly aligned.

Clean & lubricate the fan motor and bearings

1. Find the fan motor and bearings, which are typically near the fan assembly.
2. Use a soft brush or cloth to clean any dust and debris from the motor and bearings.
3. If needed, apply a few drops of lubricant (machine oil or silicone spray) to the motor and bearing surfaces. Avoid over-lubricating since this can attract more dirt and debris.

Examine the compressor for potential issues

1. Find the compressor, which is usually a large, cylindrical component in the unit.
2. Inspect the compressor for any visible damage such as cracks or leaks.
3. While the unit is running, listen for any unusual sounds coming from the compressor. If you hear grinding or loud buzzing noises and suspect a failing compressor, don’t attempt to replace it yourself. Contact a licensed HVAC technician for further assistance.

Check the fans

Your unit may have multiple fans, including an evaporator fan and a condenser fan. Look over the fan blades near the condenser for any signs of damage like cracks, chips, or bends. If the blades are damaged, replace them with new ones that are compatible with your unit. Make sure the fan blades are properly aligned and balanced. Misaligned blades can cause excessive vibration and noise while the AC is running. The evaporator fan will be located deeper inside the unit.

Read more: What is a Ductless Mini-Split Air Conditioner And How Does it Work?

3. Water is leaking from the unit

Do you see wet spots or water leaking from your AC unit? Here’s what to try:

Inspect & clean the condensate drain

1. Find the condensate drain, which is at the base of the unit or near the evaporator coil.
2. Remove any debris or dirt that may be blocking the drain hole.

For stubborn clogs, use a wet/dry vacuum or a flexible brush to clear the obstruction.

Check for proper installation and leveling

1. Look around the unit to make sure it’s installed correctly with a slight tilt towards the outside to allow for the drainage of condensate.
2. Inspect the mounting brackets and window frame for any signs of damage or warping that could affect the unit’s angle and stability.

Examine and replace damaged or worn seals

Inspect the seals around the unit – both inside and outside the window – for any signs of wear or damage. Replace them as needed to keep a good seal and prevent water leakage.

Consider using a dehumidifier

If you’re using a window air conditioner in an area with extremely high humidity, the unit might experience excessive condensation. If this is the case, consider using a dehumidifier in the room to help reduce humidity levels and excess condensation.

4. The AC won’t turn on or turns on and off

If your window AC unit isn’t turning on, is shutting off unexpectedly, or has flickering lights, follow these steps:

Check for a blown fuse or tripped circuit breaker

1. Find your home’s electrical panel and identify the breaker or fuse associated with the air conditioner.
2. If the circuit breaker has tripped, reset it by flipping it off and then back on. If the fuse is blown, replace it with a new one of the same amperage.

Check the power cord

1. Examine the power cord for any signs of damage such as fraying, loose connections or exposed wires.
2. If the cord is damaged, unplug the unit and replace the power cord with a new one that’s compatible with your air conditioner model.

Check the control board

1. With the unit unplugged, remove any covers or panels necessary to access the control board and wiring.
2. Inspect the contacts and wiring for any signs of corrosion, damage, or loose connections. If you find any damage, replace the wiring or control board as needed.
3. Tighten any loose connections.

Read more: How to Clean Your Air Conditioner the Easy Way

5. There’s ice forming on the unit

A frozen window air conditioner can be caused by restricted airflow or low refrigerant levels.

1. If there’s excessive ice or frost on the evaporator coils, let the air conditioner remain unplugged for a few hours or overnight so the ice or frost on the evaporator coils can melt completely. You can place towels or a tray underneath the unit to catch any water that may drip.
2. Check the air filter and clean or replace it if needed.
3. Look over the vents and coils to make sure they’re clean and unblocked.

If the problem persists, you may have a refrigerant leak. In that case, you’ll need to contact a licensed HVAC technician due to refrigerant handling regulations.

Additional information

Thank you for reading! We hope this guide helped you get your window AC unit 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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