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Why Is Your Window AC Not Blowing Cold Air? 5 Reasons Why and How to Fix It
Identifying why your window AC isn't blowing cold air is the first step in restoring comfort to your living space. Troubleshooting a window AC unit yourself can help you determine if it's a simple problem such as a clogged filter or a more complex issue like a control panel. Then, if you're unable to fix the AC unit yourself, you can at least decide whether it's best to call a professional for repair or replace the unit.
Below, we've laid out some common reasons a window AC may not blow cold air, plus some troubleshooting tips for fixing the problem yourself.
Clogged Filter
Like a full-size HVAC unit, a window air conditioner relies on ample airflow throughout the system to function properly. Lack of airflow due to a clogged filter can drastically reduce the system's ability to adequately cool the air, resulting in warm air blowing from the vents.
Start by thoroughly cleaning the filter before moving on to more troubleshooting steps.
Tip
Be sure to check around the air intakes on the machine to ensure there is no debris blocking them.
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Inadequate Airflow
While a clogged filter is the easiest window AC airflow problem to troubleshoot, it's not the only one. Poor airflow due to a broken fan blade or a faulty fan motor can also result in a lack of cold air blowing from the unit. Issues with the window fan motor are often paired with a clunky noise.
: AC unit maintenance tips to keep the cool air coming (FOX 32 Chicago)
If the fan and fan motor seem to be operating normally, the inadequate airflow could be a result of a blocked evaporator coil, which happens as a result of dust and debris reaching the inside of the unit. You can typically access the evaporator coil by removing the front panel, allowing you to gently clean it using a vacuum and a brush attachment.
Control Panel
A window AC unit's control panel is the brain that tells each component when and how to work properly in order to blow cold air. If you've failed to identify a faulty component or simple underlying cause for your window AC blowing warm air, the issue may lie in the control panel.
While not impossible for a DIYer, replacing a window AC control panel yourself is significantly more involved than cleaning a filter.
Temperature Control
Anyone who has used a window air conditioner knows that you 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 (thermal resistor), which is essentially a temperature-controlled switch. The thermistor measures the air around the evaporator and shuts off the system when it reaches the threshold set by the thermostat. If the thermistor is faulty, the unit will not cool the air properly.
If you're familiar with electrical functions and repairs, you can test the thermistor by placing an ice cube on the thermistor and checking the continuity using a multimeter. Luckily, replacing a window AC thermistor is usually even easier than testing one, so you can likely knock out this repair yourself.
Malfunctioning Cooling System
If you've failed to identify a simple cause of your window air conditioner blowing warm air, there could be a more complex issue with the cooling system such as a faulty compressor or a lack of refrigerant. However, if a window AC is low on refrigerant, this means there is damage causing a leak.
While many window air conditioners can technically be recharged, they're designed to last their entire lifespan with just the refrigerant that's included in the system at the time of purchase. While it's not guaranteed, your window AC needing a recharge may be indicative that it has reached the end of its lifespan and isn't worth fixing.
When to Call a Professional
If you've determined that your window AC unit's fault is too complex to fix or you can't pinpoint the issue, it may be time to call a professional to repair the unit. However, this could easily cost upwards of $200 depending on the severity of the issue, which may not be justifiable, when it's possible to find comparable replacements for a similar price.
While the decision will come down to the size, age, and quality of your window AC unit, it may be time to replace it rather than repair it.
Frequently Asked Questions
Should you turn off the AC if it's not cooling?
If your AC unit isn't cooling and you're unable to identify the underlying issue, it's best to turn off the unit before the problem worsens. When an AC unit begins to blow warm air, it doesn't mean it's totally broken.
However, continuing to use it in a compromised state can damage individual components, leading to more costly repairs. As soon as you notice your air conditioner struggling to cool your home, turn it off and contact an HVAC service technician.
Why is your window AC turning on but no air is coming out?
If you hear your window AC unit turning on but can't feel air blowing out of it, it likely has a faulty fan motor.
If there is a small amount of air blowing from the unit, this could be due to restricted airflow from a dirty filter, blocked air intake, or a bent or broken fan blade.
How to help a window AC cool better?
The best way to help a window AC cool better is by staying on top of cleaning the filter, air intake, and coils. This will allow the system to run smoothly and cool the air more efficiently. You can also maximize a window AC unit's efficiency by closing curtains, sealing windows, and cooking inside less often.
