Recharging a Window AC: Steps and Precautions

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Refrigerant recharging on a window air conditioner isn’t often done because most people replace their units when they fail.

Windows air conditioners may be recharged with refrigerants and put back to use to cool a space or room. Learning how to do it safely will save you a lot of money.

It’s not hard to recharge a unit, but if you don’t know anything about HVAC refrigerant, then make sure you learn about that before you start.

There are two ways to recharge an air conditioner: the low-cost backyard quick method used by many homeowners or a more involved but recommended technology method.

The low-cost backyard technique is the most used method for recharging a window air conditioner if it’s low on coolant, but not recommended.

Here are the steps for both types of recharging methods.

Parts required:

  • Bullet Valve
  • Refrigerant Normally R410a
  • HVAC Gauges or Recharge Hose

Backyard Quick Method To Recharge A Window A/C

  • Connect a Bullet Schrader Valve to the low-pressure line of your car.
  • Join the refrigerant flowing into the hose.
  • Connect the charging hose to the Schrader valve.
  • Push refrigerant into the systems to open the valve on the recharge hoses.

Attaching a Bullet Valve

recharging window ac

A bullet valve is an easy way to add a recharger port into an air conditioner. Most window air conditioners do not have a service port that is easy to access for taking out a low-cost bullet valve.

An Allen Valve Wrench is easy to use to secure the screws onto the bullet valve. It includes a sharp needle that goes into the line, usually connected to the lower pressure refrigerant line.

You’ll need an HVAC gauge or a recharging hose too.

Refrigerant Type

The type of refrigerant used will be labeled on the machine. Most older units use R22 refrigerant, which is no longer manufactured. Newer units usually use R410A refrigerant.

Many websites and YouTube videos show people using R134a refrigerant for recharging window AC units.

They should never be mixed when charging refrigerants because no machine is designed for mixed-medium refrigerants. As for the oils used in HVs, they may vary and ruin the compressor or other parts.

Many YouTube videos say they successfully use R134a in R410a and/or R22 systems, but we wouldn’t recommend that. Follow the instructions provided by the manufacturer. Don’t use anything else.

People use R134A because it’s widely used in automobile air conditioning systems and cheap to buy online and at auto parts stores.

Refrigerant Pressure

recharging window ac

Each HVAC system requires different air pressure depending upon the temperature. Every window air conditioner requires the right pressure to cool properly.

If a device has low refrigerant, the pressure inside the device will be too low and won’t work. If a device is filled up, the pressure will be so high that the machine won’t work.

Therefore, it’s important to get the pressure right before adding refrigerant so that you don’t overfill the unit. It is recommended to keep the pressure below 40 psi on the low-pressure side before testing the device and checking if it starts to cool.

Starting at a lower pressure, such as 30 psi, is best, and testing the unit for cool­ing. If the unit isn’t cooling, slowly increase the pressure until it starts working again. You’ll need a recharge hose or an HVAC gauge with a pressure age.

How To Recharge a Window A/C (Recommended Method)

1. Find and Repair Any Leaks

recharging window ac

The very first step is to check for leaks. If a window unit leaks slowly, it will only need a small boost every few years. It’s not a big deal if you want to run the air conditioner like that.

A fast leak must be repaired and fixed before it can be refilled.

There are several ways to find leaks, from a visual inspection to filling a system with nitrogen and using soap to find them.

Refrigerant leak detectors can also be purchased, and they make a loud, clear beep when they detect refrigerant leaks. Leaks often occur at joints. If you find a leaking joint, it often requires repairing it by resoldering it together.

2. Install a Service Port (Schrader Valve)

Small air conditioners don’t usually have a service port to connect gauges. Installing a simple service line involves soldering at a port, using a piercing valve kit, or both.

It’s easy to install a Schrader valve on a device. Most people use a piercing valve to install Schrader Valves. Service vents are often installed on the high-pressure line to add more refrigerant. That’s the larger size.

3. Recharge the Unit

recharging window ac

Once leaks are repaired and a new service port has been installed, it is time for the new refrigerant. You need an HVAC gauge and a good refrigerant.

Most devices use R410A today, but check the device’s service label for any restrictions. You can purchase R410A at air conditioning supply stores and online.

Connect your gauge to the service interface and the refrigerant tank. Understand what the full-charge pressure setting is before beginning. Don’t overfill your unit.

Check your pressure on the gauge and a temperature-pressure graph to understand what it should be.


These are the basic steps involved in charging a window air conditioner. Remember, there’ll always be different variations between manufacturers.

Make sure to follow safety procedures when working with an HVAC unit.

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