How To Recharge A Window Air Conditioner (19-Step Guide)

Window AC

Look no further – this article will provide step-by-step instructions on how to get your window unit running smoothly again!

First things first, do window AC units need to be charged? 

Just like larger AC systems, window air conditioners can spring a leak and lose Freon over time. If this happens, it will need to be recharged to properly cool your room. Window units are closed systems, meaning they should never need additional refrigerant. If your unit does need to be recharged, it must be leaking somewhere.

The leak should be repaired before adding additional refrigerant to your unit. Otherwise what you put in will inevitably just leak back out. Keep reading to learn the 19 steps on how to put Freon in a window AC!

Preparation Tips

All refrigerant, like Freon, are dangerous to handle and you should only proceed if you’re confident and take the necessary precautions.

Make sure you’re using the correct refrigerant for your unit. Most units use R410A, but older units may use R22 more commonly referred to as Freon. Freon is no longer in production and is pretty difficult to come by.

What is still available is expensive and if your unit uses it, you may be better off replacing it with a newer model. Some of the newest units use R32.

These refrigerants cannot be mixed and are not interchangeable. You must use the correct refrigerant for your model. It will be labeled on the rating plate what refrigerant is used and how much it contains.

You cannot put R134A in a window unit, unless it is labeled and rated for it. It’s primary use is in the automotive industry and it runs at different temperatures and pressures.

Using this refrigerant in a unit that it is not rated for can be detrimental to the compressor and other components.

RELATED: How To Add Coolant To AC Unit?

Supplies & Tools

  • Safety Equipment – Safety Glasses, Gloves
  • Screwdriver – For disassembling unit to access compressor and refrigerant lines
  • Digital Thermometer – For measuring room temperature and supply air temperature
  • Refrigerant Gauges – Specific gauges for your type of refrigerant to read pressure and add Freon
  • Can Tap Valve – To pierce the refrigerant can and connect to the gauges
  • Bullet Piercing Valve – Necessary if your unit does not have a service port (most don’t)
  • Allen Wrench – Needed to open and close the bullet valve
  • Your Unit’s Specific Refrigerant – Small canister of R22, R410A, or R32

How To Add Freon To A Window Unit (19-Step Guide)

Step 1 – Determine If Your Window Unit Needs Recharged

Dirty filters and coils can imitate a system that is low on Freon. Make sure everything is clean and reset your unit. If it’s still not cooling, proceed to the next step.

Step 2 – Measure Your Room Air Temperature

Using the digital thermometer measure your room temperature. 

digital thermometer

Step 3 – Measure Your Window Unit’s Output Air Temperature

Use the digital thermometer again to measure the temperature of the air being supplied to the room from the unit.

Step 4 – Calculate The Temperature Difference

This difference in temperature can tell you if a Freon leak is the actual culprit and if you should proceed with adding additional refrigerant. 

  • More than 20°F is an airflow issue. Adding Freon will not help.
  • 18-20°F is normal. This is a proper temperature drop.
  • 10-15°F This is most likely a low charge issue and adding Freon may be necessary.
  • Under 10°F is usually a much more significant issue. Depending on the severity of the problem, you may need to replace your unit.

Read Also >> Why Does My Air Conditioner Keep Running?

Step 5 – Unplug and Remove Your Window AC 

Unplug your unit and remove it from the window. Place it on a workbench or table so that you can easily work on it.

Step 6 – Remove The Housing

Using a screwdriver, remove the screws and housing on the backside of the unit so you can access the compressor.

It usually looks like a large black cylinder and will have two copper lines connected to it.

Use this time to clean your blower and coils and make sure the drain holes in the back are clear as well. It’s a lot easier to do once everything is open.

Step 7 – Look For Leaks

With everything opened up, search for refrigerant leaks or other potential issues that need addressed.

You cannot see the refrigerant. What you can see is compressor oil. Check the lines and coils for oily residue and discoloration. 

Step 8 – Consider The Size Of The Leak 

If you are able to locate what is leaking, take into consideration if it’s repairable. If the leak is small, you may be able to use a sealant that can be added to the refrigerant to stop it from leaking.

If it is a large leak, do not proceed. You will most likely need a certified technician to make that repair, or replace the unit.

RELATED: What Should Be The Air Conditioning Setting For Summer?

Step 9 – Identify The Suction Line

The larger of the two lines connected to the compressor is called the suction line. This is the line that will be used to add Freon.

Step 10 – Attach The Bullet Valve

Follow the instructions that come with your valve. It typically mounts or “saddles” the pipe. Install it on a straight section of the suction line.

Step 11 – Install Can Tap Valve 

Install the tap valve on the refrigerant can, but do not pierce it yet.

Step 12 – Connect Gauges

Connect the blue side hose of the gauges to the bullet valve port.

Connect the yellow middle hose to the refrigerant tap valve.

refrigerant gauges

Step 13 – Pierce The Can

Turn the valve on the tap valve to pierce the can. Once pierced, open the valve back up to allow refrigerant to flow to the gauges.

Step 14 – Turn Your Window Unit On

Set your unit to run on full blast. You need to compressor to run and drop the pressure on the suction line in order to add Freon.

Step 15 – Add Freon

Once the compressor is running, open the left side of the gauge manifold intermittently. This will allow bursts of refrigerant from the can to flow to the unit.

Step 16 – Monitor The Gauge

Depending on your type of refrigerant, there’s different measurements to look for.

For R22 you want to see your pressure around 70-psi. For R410A it should be around 130-psi. 

These are rule of thumb measurements. Your particular unit cannot be accurately charged without suction and liquid line pressures and temperatures to read superheat and subcooling.

Window units are not designed to be checked in this way.

Read Also >> What Causes AC Units To Freeze Up?

Step 17 – Close Your Valves

Once you’ve added enough Freon, close the bullet valve you installed on the suction line and close the tap valve on the can.

Step 18 – Check Temperature

Using the digital thermometer, check for a proper temperature difference. Again, it should be around 20°F.

Step 19 – Disconnect And Reinstall

With all your valves closed, you can disconnect your hoses and replace the window unit housing. Reinstall your unit in the window and your done!

Is Recharging Your Window Unit Worth It?

This is a pretty common question I get and my honest opinion is, in most cases, no.

If you were to purchase everything you need to make this repair, (gauges, refrigerant, bullet valve, etc.) you can almost buy a new window unit.

Sometimes you can buy a window AC recharge kit, but those are pretty pricey as well when using R410A. Most of the inexpensive ones are for automotive repairs and cannot be used on window units.

Keep in mind, this is most likely a temporary fix and if the leak wasn’t repaired, it will have to be filled again.

In most places, you also have to be EPA certified to purchase and handle these types of refrigerants.

This is a potentially dangerous repair that will most likely have to be done again in the future. My recommendation is to seriously consider replacing your window unit unless repairing it is your only option.

Read Also >> Why Does My Air Conditioner Smell?

Frequently Asked Questions 

Can You Add Freon To Window AC Units?

Yes. Although most aren’t set up to be serviced, you can install your own valve and port and recharge your unit with the correct refrigerant as long as you have the tools and knowledge.

How Long Does Freon Last In A Window AC?

Window air conditioners are closed systems, so the refrigerant should never leak out and should last the life of the unit. Unfortunately, parts fail and things break.

Corrosion or physical damage can cause coils and lines to leak, but the average lifespan of a window unit is about 8-10 years.

Why Is My Window AC Not Cooling?

The most common reasons for a window unit to not cool is dirty filters and coils.

It could also be leaking Freon or it may have an electrical or mechanical failure. Regular maintenance is very beneficial in preventing your unit from breakdowns.

Why Is My Window AC Blowing Cold Air But Not Cooling The House?

If your window AC is blowing cold air but not cooling the house, you probably have restricted airflow or your unit is too small.

Make sure your filters are clean and your fan is on high speed, and if the problem persists, it may be too small of a unit to handle the heat load of that room.

Final Thoughts

If you are considering this type of window AC repair, make sure you rule out all other potential causes before attempting this.

If you’re questioning whether it’s worthwhile or if it’s something you can handle, don’t risk it. If you aren’t careful you can damage your equipment or injure yourself. Either call a professional or replace the unit if you aren’t 100% certain you can do this.

Thanks for reading!

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