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How to Put Freon in a Window AC Unit

As the summer season sets in, ensuring your window AC unit works optimally becomes a priority. Over time, your AC unit’s Freon (or refrigerant) level might drop, affecting its efficiency. If you’ve noticed that your unit is not cooling as effectively as it used to, it might be time to add some Freon. This guide will walk you through the steps to safely and effectively add Freon to your window AC unit.

Do Window AC Units Need Freon?

Window AC units use refrigerant to cool the air; freon is one type of refrigerant. However, most modern window AC units use a different type of refrigerant called R-410A, which is more environmentally friendly and efficient. If your window AC unit was manufactured before 2010, it may use freon, also known as R-22. You can check the label on your unit to see what type of refrigerant it uses.

Window AC units do not need freon unless there is a leak in the system that causes the refrigerant level to drop. If your window AC unit is not cooling well or making strange noises, it may need a refrigerant recharge. However, it would be best not to put freon in a window AC unit that uses R-410A or vice versa, as this can damage the unit and reduce its efficiency.

You should also not attempt to recharge the refrigerant yourself unless you have the proper tools and skills, as this can be dangerous and illegal. It is better to hire a professional to do it for you.

How to Put Freon in a Window AC Unit

Before proceeding with adding refrigerant (often referred to as “Freon,” which is a brand name) to a window AC unit, it’s essential to note a few things:

  1. Legality: In many places, especially in the U.S., only certified technicians are legally allowed to handle, add, or recover refrigerants due to environmental concerns and potential hazards. Always check local regulations and laws before attempting any work involving refrigerants.
  2. Safety: Refrigerants can be harmful if inhaled or if they come into contact with the skin. They can also cause frostbite. Always work in a well-ventilated area and wear safety gloves and goggles.
  3. Diagnosis: If your window AC unit requires refrigerant, it indicates a leak. Merely adding refrigerant without addressing the leak is a temporary solution. The leak should be identified and repaired first.

If you still wish to proceed, here’s a general guide on how to add refrigerant to a window AC unit:


  • Refrigerant (appropriate type for the unit)
  • Gauges and hoses designed for the specific refrigerant type
  • A piercing or saddle valve (to access the refrigerant lines without cutting)

Steps to Put Freon in a Window AC Unit:

  1. Turn Off the Unit: Always turn off and unplug the window AC unit before starting any work.
  2. Access the Refrigerant Lines: Most window AC units have two lines, a larger low-pressure line and a smaller high-pressure line.
  3. Attach the Piercing Valve: If your unit does not have service ports (most window units won’t), you must attach a piercing or saddle valve to the low-pressure line to add refrigerant. Follow the manufacturer’s instructions for attaching the valve.
  4. Connect the Gauges: Attach the blue (low side) hose of your gauge set to the service port or piercing valve. Make sure the connection is tight to prevent any leaks.
  5. Check the Pressure: Turn on the AC unit and let it run for a few minutes. Read the pressure on the gauges. Consult the unit’s specifications to determine the correct pressure.
  6. Add Refrigerant: If the pressure is lower than the unit’s specifications, you can start adding refrigerant. Connect your refrigerant can to the yellow hose on your gauge set. Open the valve on the refrigerant can and slightly open the blue (low side) handle on your gauge set to allow refrigerant to flow into the unit. Add slowly and periodically close the valve to check the pressure. Do not overcharge.
  7. Check the Cooling: After adding the necessary refrigerant, let the unit run and check if it’s cooling more effectively.
  8. Remove the Gauges: Once you’re done, carefully disconnect the gauges, ensuring that no refrigerant is released into the atmosphere.
  9. Monitor the Unit: As mentioned, adding refrigerant indicates there was a leak. Monitor the unit to ensure it continues to function correctly. If the cooling diminishes again, you likely have an ongoing leak.

It’s always recommended to consult with a professional HVAC technician if you believe your window AC unit requires refrigerant. They have the tools, expertise, and certifications to address the issue properly and safely.

Who Puts Freon in Window Air Conditioners?

In the US, homeowners can put freon in window air conditioners themselves, but they need some general knowledge and specific tools to do it correctly. However, the Environmental Protection Agency (EPA) requires anyone who hires someone else to do the job to have a professional certification. 

You can find certified HVAC technicians online or in your local area who can put freon in your window AC unit. However, you should not put freon in a window AC unit that uses a different type of refrigerant, such as R-410A, as this can damage the unit and reduce efficiency. You should also check the label on your unit to see what type of refrigerant it uses before putting freon in it.

Where Do You Put Freon in a Window AC?

To put freon in a window air conditioner, locate the freon inlet valve on the back of the unit. You must also remove the front panel to access the coils and the service valve near them. Using a yellow tube, you need to connect a gauge manifold and a freon bottle to the service valve. 

You need to turn on the unit and open the left side of the gauge manifold intermittently to allow bursts of freon to flow to the unit. You must monitor the unit’s pressure and temperature using the gauges and a thermometer. You need to stop adding freon when the pressure and temperature reach the optimal levels for your unit.

This process can be dangerous and complicated, so you should only do it with the proper knowledge and tools. Otherwise, you should hire a professional to do it for you. You should also make sure you use the right type of freon for your unit, as using a different type can damage the unit and reduce its efficiency. You can check the label on your unit or the specification sheet to see what type of freon it uses.


Ensuring the right amount of Freon in your window AC unit is crucial for its optimal performance and lifespan. With the detailed steps provided above, we are confident you can easily handle this task. However, it’s always best to consult a professional if you’re unsure about any part of the process or face difficulties.