Why Is Your Window Air Conditioner Not Blowing Cold Air? 5 Reasons Why

Determining why your window air conditioner isn’t blowing cold air is the first step to restoring comfort to your living space. Troubleshooting your window air conditioner yourself can help you determine whether it’s a simple problem like a clogged filter or a more complex issue like a control board. Then, if you can’t fix the air conditioner yourself, you can at least decide whether to call in a professional to repair or replace the unit.

Below, we’ve outlined some common reasons why a window air conditioner isn’t blowing cold air, along with some troubleshooting tips to help you fix the problem yourself.

Filter is clogged

Like a large HVAC unit, a window air conditioner relies on adequate airflow throughout the system to function properly. A lack of airflow due to a clogged filter can significantly reduce the system’s ability to adequately cool the air, resulting in warm air blowing out of the vents.

Start by thoroughly cleaning the filter before performing any other troubleshooting steps.

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Insufficient air flow

While a clogged filter is the easiest window AC airflow problem to fix, it is not the only problem. Poor airflow due to a damaged fan blade or a faulty fan motor can also result in the unit not blowing cold air. Problems with window fan motors are often accompanied by an unpleasant noise.

If the fan and fan motor appear to be operating normally, insufficient airflow may be caused by a blocked evaporator coil, which occurs when dust and debris gets inside the unit. You can usually access the evaporator coil by removing the front panel, allowing you to gently clean it with a vacuum cleaner and brush attachment.

Dashboard

The control panel of your window air conditioner is the brain that tells each component when and how to operate properly to blow cold air. If you can’t identify a faulty component or a simple underlying cause for your window air conditioner blowing warm air, the problem may lie in the control panel.

While not impossible for the DIYer, replacing a window air conditioner control panel yourself is much more complicated than cleaning the filter.

Temperature control

Anyone who has ever used a window air conditioner knows that you can set the temperature right on the front of the unit, but how does it know when to turn on and off?

A window AC unit uses something called a thermistor, which is essentially a temperature control switch. The thermistor measures the air around the evaporator and shuts down the system when it reaches a threshold set by the thermostat. If the thermistor fails, the unit will not cool the air properly.

If you are familiar with electrical functions and repairs, you can test the thermistor by placing an ice cube on the thermistor and checking for continuity with a multimeter. Fortunately, replacing a window AC thermistor is often easier than testing the thermistor, so you can do the repair yourself.

Cooling system failure

If you can’t determine the simple cause of your window air conditioner blowing warm air, there may be a more complex problem with the cooling system, such as a faulty compressor or a lack of refrigerant. However, if your window air conditioner is low on refrigerant, this means there is a leak.

While many window air conditioners can technically be recharged, they are designed to last their entire life with only the refrigerant that was in the system at the time of purchase. While not guaranteed, the need for a recharge on your window air conditioner may indicate that it has reached the end of its life and is not worth repairing.

When to call a professional

If you determine that your window air conditioner is too complicated to fix or you can’t pinpoint the problem, it may be time to call a professional to repair it. However, this can easily cost upwards of $200 depending on the severity of the problem, which may not be reasonable when you can find a comparable replacement for the same price.

While the decision will depend on the size, age, and quality of your window air conditioner, it may be time to replace it rather than repair it.