How To Recharge A Window AC? Refill Freon In Window AC At Home (DIY)

How To Recharge A Window AC Unit

Are you thinking of recharging your Window AC unit (with Freon) and wondering exactly how to go about it- I’ve got you covered. 

Usually, window Air Conditioners have a refrigerant system that is very tight and closed. Unfortunately, things go loose and haywire as they get old, and this is the case with refrigerants as well, which might often lead to a leak in the refrigerant. 

The refrigerant lines, which are filled with Freon, start losing it. So, essentially, recharging a Window AC unit means that you’ve got to find the leak, refill the Freon, and recharge and rebind it so that your AC unit can keep functioning well. 

Before anything, you might want to do a general check-up of your unit to ensure that none of the other parts need any brushing up in the repair or replace department.

You may find problems with the Air filter being too dusty, or the fan needing to be tightened. So make sure to spend time on these small fixes along the way to keep your AC in tip-top shape.

So In this guide, we show you a couple of steps to help your AC revert to being fully functional again.

Things To Consider Before Refilling Window AC Unit: Safety

Before embarking on the process of recharging the AC, make sure to take all the right steps to ensure your own safety. Recharging an AC can cause you to tamper with some potentially risky internal parts.

In fact, some states in the US even have laws prohibiting non-professional technicians from indulging in this practice. Verify what the status of this law is in your own state before proceeding.

  • Once you know that you’re legally allowed to partake in the recharging process, start by gathering your materials. To ensure maximum safety, get supplies like Protective glasses, gloves, and so on.
  • Make sure that the unit is unplugged from the power outlet.
  • Keep all the materials you need to open up the unit near you. Things like the Refrigerant, Freon Kit, Screwdriver, are tools necessary for the progress of the process. And other safety/protective wear like insulated rubber gloves, safety sunglasses, etc.

What Is Recharging Your Window AC unit all about?

If you’re still a little unclear about why your AC unit needs recharging- here’s the deal.

Every AC runs on something called the ‘refrigerant’ which passes through the evaporator coils of your unit. The refrigerant is at very low and chilling temperatures and is largely responsible for extracting humidity from the hot air intake from your room and cooling it before it is sent out.

The refrigerant liquid in an AC is something that doesn’t really concern the homeowner, as it is designed to support its unit till the end of its lifespan.

However, when cooling in the air from your AC starts to noticeably lessen, it is a sign that your refrigerant levels have dropped due to a ‘leak’ in the coils.

Consequently, you will have to take the steps required to firstly- verify whether your AC unit’s refrigerant/Freon levels are actually low. Two, the source of the leak has to be found out.

Finally, the refrigerant lines have to be reimbursed with the right amount of Freon to bring the AC back to shape.

How To Recharge Your Window AC? Step By Step Guide

This process of recharging your Window AC unit is detailed as follows:

Warning: Recharging Your Window AC by yourself can be a Risky Job. If you know nothing about the process (or you’re a complete beginner). Make sure you’re following every safety protocol. Be Safe

STEP 1: Checking for Low Refrigerant Levels

Low refrigerant levels are naturally reflected in the AC’s performance and efficiency- as they are lowered. Now, the extent of this lowering may vary from AC to AC depending on its condition, years of use, and frequency of use.

However, it is optimum that there is at least a mid-level drop of the output temperature to diagnose your AC with this problem.

First, you’ll have to test this theory by comparing the output airflow temperature of the AC to the room temperature. By doing so, you’re examining how much of a difference your AC is able to make from the room temperature to make your surroundings cooler.

If the result is a mid-level difference, you can attribute the cause to the refrigerant levels.

Follow the steps for Checking Low Refrigerant Levels:

Measuring the Output Airflow Temperature

You will need a thermometer for this. Place the digital thermometer as close to the AC as possible, and wait for up to a few seconds to a minute to get an accurate reading of the temperature.

Generally, if lesser cooling from your AC is noticeable in the airflow even without the thermometer- you can take it as an indicator of the problem.

Measuring the Room temperature

Next, use your thermometer to measure the room temperature as accurately as possible.

Find the Difference in Temperatures

Finally, you can conclude the process by subtracting the Window AC airflow output temperature from the room temperature as measures.

Typically, any result that shows that your air conditioner is able to create a difference of 20 F or higher means that there is no problem with the refrigerant.

This is a low-level difference. If the difference is between 10F and 20 F- a mid-level difference- your window AC refrigerant is in need of recharging.

Lastly, if your readings show an even lesser difference of below 10 F, note that your AC’s operating power is significantly low and might need to be checked by a professional.

STEP 2: Identify and Fix the Freon Leak

The process is to be kick-started by first inspecting the state of your refrigerant. To do this, you’ll have to open up your air conditioner and examine the refrigerant lines lying inside.

Some ACs are easy enough to open with a simple screwdriver. Older ACs may have ways by which you can simply slide away the front ends of the unit to access the internal parts.

The main components you will be focusing on to address the problem are- the compressor and the refrigerant lines. The refrigerant lines are two lines that emerge from the compressor.

These carry liquids that are very low in temperature and are running at extremely high pressure, so you have to be careful in their handling as you check for the source of the leak.

STEP 3: Checking for the leak

One of the easiest ways to detect a leak is to simply trace the path of the refrigerant lines. You might stumble across a clump of refrigerant collected right below the leak.

While plain old observation can do the trick, there are other verified ways to assure the presence of a leak. Most HVAC professions don’t depend only on what appears to the eye. They use methods like:

1. A mixture of soap and water, which when applied to the refrigerant transmission gear- stimulates the place of the leak to bubble up as a reaction.

2. Nitrogen is also used to check if the refrigerant pressure is high or low. Nitrogen is pumped into either one of the refrigerant lines. The pressure created at the start is compared to the pressure after a few minutes. If there is a visible decrease, there is a leak.

3. The fluorescent dye method is another popular way by which dye is filled within the systems and is allowed to run throughout when the unit turns one. If you use a flashlight, areas with leaks will start glowing to indicate their presence. You can also use a leak detector to recognize the source of a leak.

STEP 4: Close up the leak

Before recharging the unit, you must first ensure that the leak is fixed. You can solder in the place of the leak, or use Freon Leak repair kits that are available easily in stores.

This is especially effective for small AC units and leaks. Leak repair kits operate by way of Freon Injection, and this generally improves the refrigerant levels.

STEP 5: Inspect What Type Of Refrigerant Your Window AC Uses

The last stages of this process require actually recharging the refrigerant. Make sure that the refrigerant you’re inputting is exactly the requirement of your AC.

You’ll find the refrigerant specifications in the manual booklet of the unit, where it will show if your unit runs an R410A type liquid or an R22 liquid, and so on.

One way to do this would be to use a tap valve and an optional service valve to conduct the next steps. You can purchase them in your local hardware store, or you might even find them included in your Freon kit.

Locate the compressor and the two refrigerant lines emerging from it. The tapped valve needs to be attached to the bigger refrigerant line, which will often have a line that says ‘Add Freon Here’ on it.

The other line is to be connected to the Service valve. Following this, both the valves need to be attached to the Freon container which is to be placed right in between them.

STEP 6: Release Excess Air From Refrigerant Line

Usually, when refrigerant levels go down due to a leak, the air gets into the refrigerant lines, and it needs to be removed before Freon can be refilled.

For this, you need a blue tube that is to be connected to the Tap Valve and the Compound Gauge. Then, take the accompanying yellow tube and ensure that it is attached to the Freon container.

With the tubes and gauges properly attached, you can turn on the AC and set it to the fastest fan speed setting available. This gets the refrigerant running as well.

Loosen up the yellow tube near the gauge slightly for about two seconds, and this will push out all the air from your refrigerant lines.

Note that gauge sets are also available to be bought, and must be done in accordance with their compatibility with your AC’s refrigerant liquid type.

STEP 7: Refill Freon In Your Window AC Unit

Finally, you can recharge your AC with Freon. If you are using the tap-service valve connection, you simply have to turn on the unit and run it at a high setting.

This will cause the Freon to naturally start flowing from the container to the refrigerant lines through the valves. Once the required Freon limit has been reached, turn off the AC.


This concludes the process of recharging your Window AC unit. Ensure maximum safety by turning off the unit properly, unplugging it, and removing all the valves, tubes, and gauges before further use.

Your newly recharged Window AC unit not only guarantees more efficient performance but also elongates your AC’s lifespan and saves you the trouble of replacing the entire unit. By recharging, your Window AC is as good as new!

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