Window air conditioners are popular models as they are convenient to install, relatively affordable compared to other AC types, and efficient in cooling moderately-sized rooms. A window air conditioner is also easier to clean and maintain.

However, window ACs are not immune to malfunctions, and one common issue with window air conditioners is blowing warm air instead of cold air. This issue often indicates an underlying problem with your window AC unit, so it is imperative to find and fix the root cause of the problem to maintain the condition of your window AC.

Causes of Window Air Conditioner Not Blowing Cold Air

Reason #1: Restricted Air Flow

Most window air conditioners encase the entire cooling system in one housing, which causes the parts to be tightly packed into the same frame. Even slightly filthy air filters can already cause poor air flow to circulate around the unit, and cause the warm or room temperature air to rotate back indoors.

Your window air conditioner may have blocked vents, debris buildup, or a dirty aircon interior, which will require an experienced technician to properly clean each part. Restricted airflow often occurs when the unit is improperly cleaned, or is not cleaned regularly, allowing dust and dirt to clog the vents.

Reason #2: Faulty Fan Motor or Fan Blades

Another common reason for an air conditioner not blowing cool air is a busted fan. The motor may be in need of replacement as it can no longer function as normal. A faulty fan motor will cause restricted air flow, which will also cause a window air conditioner blowing warm air instead of cool air.

Alternatively, the issue may lie with bent or broken fan blades. The blades may have broken off, causing irregular air flow, or the blades might need to top up with lubricant to spin smoothly. You may hear clunking or rattling sounds from your AC unit, which connotes a part that has broken off, and is rattling around the interior of your unit.

Reason #3: Dirty Evaporator Coils

The evaporator coils are responsible for delivering the cooled air into your room, but when these coils are caked in dirt, they can no longer properly cool the air. A dirty evaporator coil shows symptoms such as a warm aircon unit, as well as a leaking unit. If you notice these two symptoms together, then you most likely have an issue with the evaporator coil.

Reason #4: Issues with the Outdoor Side

Most AC types have an outdoor unit, also called a condenser unit, that releases the warmed air outside. A window AC unit would have a similar exhaust system connected to the indoor unit, and when this side gets clogged or malfunctions, then it can cause the warm air flow to circulate back indoors.

Your window AC may have issues with the compressor, outside fins, or vents that are causing your unit to malfunction. Cleaning the condenser unit usually fixes the issue, but advanced problems may require the expertise of a licensed HVAC technician.

Reason #5: Low Refrigerant Levels

The coolant is what turns the room temperature air into cold air flow, and when refrigerant levels are low, your window air conditioner cannot properly cool your room. Topping up the refrigerant levels will immediately fix the issue, but if your coolant seems to run out often, then you may have a leak in the refrigerant line.

Troubleshooting Guide

Fix #1: Clean the Air Filter

Clean the air filter once every two weeks - more if you use the aircon often. You can easily clean the filter at home with some soapy water, and a soft-bristled brush to scrub the dirt away. Allow the filter to air dry completely before placing it back into your unit. You may also use a vacuum cleaner with the nozzle attachment to clean the filter using a dry method.

Fix #2: Replace Fan Motor or Blades

If you hear a clunking, rattling, or helicopter-like sound, then the issue may be with your fan. You can opt to crack open the housing to check the fan motor or blades, and bend any misaligned blades back to their original position, or add lubricant to a rusted blade.

However, if you have no knowledge or experience in repairing household appliances, we recommend contacting one of our Luce Aircon technicians instead to avoid further damage to your unit, and to ensure the diagnosis of the problem is accurate.

Fix #3: Clean the Evaporator Coils

Like the filter, you can access the evaporator coil by opening the front panel vents of your AC unit. You can then use a vacuum cleaner with the nozzle attachment, or a can of compressed air to rid the coils of dirt. Avoid cleaning the coils with harsh chemicals, and make sure the coils are completely dry before using the unit.

Fix #4: Inspect the Condenser Unit

Check the outdoor side of your AC unit. You may find large pieces of debri blocking the vents, or birds may have built a nest in the warmth of your aircon. Simply remove the debris using a spray of water, or pick them off by hand. If the issue lies in the interior of your condenser unit, however, it would be better to leave repairs to the professionals.

Fix #5: Top Up Refrigerant

Contact us at Luce Aircon to top up your coolant levels, as well as diagnose, find, and repair any leaks that may be in your refrigerant lines. Refrigerant is a harsh chemical, and should not be handled at home. Our friendly technicians will be more than happy to help you with your aircon maintenance!

When to Call the Professionals?

With air conditioners, there are some easy fixes that can be done at home: such as adjusting the temperature control to the desired temperature, cleaning the air filter, or hosing down the outdoor unit. However, it is best to call for professional cleaning and maintenance services when the solution deals with the interior of the unit.

Our Luce Aircon technicians are well-versed in the common issues of multiple air conditioner brands and models across Singapore. We can assure you only the best in aircon services, as we provide quality cleaning, maintenance, inspection, and repairs for your air conditioning unit!

Check out our article on aircon not blowing cold air!