How to Add Freon to AC?

Figuring out how to add freon to AC units is a complex task. What’s worse, it’s also a bit risky – not performing the whole procedure well can result in anything from harming your AC unit to harming your home and yourself.

So, before we start, our first and main advice is to call a professional unless you’re 100% sure you know what you’re doing. While adding freon to your AC yourself is perfectly legal in the US, all AC technicians are required to undergo intensive training and certification before they can do so legally.

But, if you’re adamant about doing it yourself or you just want to learn how to put freon in window AC unit or wall AC unit for knowledge’s sake, here’s our quick step-by-step guide.

Make sure the lack of freon is the problem

If your AC is blowing warm or hot air, one possible cause of the problem is the lack of refrigerant. It could also just be a thermostat issue, however. So, before you add any freon you need to be sure the issue is not in the thermostat instead.

Even if the problem is in the lack of coolant, you need to check if there aren’t any leaks – if the pipes and coils inside the AC are covered with ice and frost, you most likely have a leak on your hands. In that case, simply adding more freon to your leaking system is unnecessary and you should just call a professional to fix the leak first.

Do the necessary preparations before adding the refrigerant

Before we get to learn how to put freon in window air conditioners or other types of AC systems, we must first cover the necessary prep time. Here’s what you need to do:

  1. Schedule a professional maintenance check-up on your AC or perform one yourself. Before you do anything you should make sure that the AC’s blower wheel, air filters, condenser coil, and evaporator coil are all in good condition and properly cleaned. If you add more refrigerant to a dirty AC you can damage it.
  2. Pick the right refrigerant. Each type and model of AC unit has its own refrigerant. Mismatching the two can lead to accidental combustion, property damage, and physical injuries. Check with the AC manufacturer on what refrigerant you need for your model. If you’re not certain, call a professional technician. R-22 and R410A are the two most popular types of refrigerants but they can’t be interchanged and there are some other types out there too.
  3. Check the temperature outside. If it’s at or below 55°F (12.7°C) you should NOT add any freon to your AC. The reason being that refrigerant seeks out cold temperatures so if the weather outside is too cold the freon will seep toward the outer unit and it won’t behave properly. Wait for warmer weather instead.
  4. Get some protection. Using safety goggles & mask is a must when handling freon as is wearing thick rubber gloves and body protection. You should never ever inhale freon nor have it fall anywhere on your skin.

Add the refrigerant to the AC unit

If you’re ready to begin and you’re sure you don’t want professional help, the process goes as such:

  1. Turn off your AC unit at both the thermostat and the breaker.
  2. Hook up the refrigerant gauges to the valve connections of the AC. Attach the blue gauge to the left-side low-pressure valve and attach the red gauge to the right-side high-pressure valve. The center valve must be left open for now, that’s where you’ll connect the yellow gauge later on. Do not open any of the valves yet!
  3. Turn on the AC for about 15 minutes. This will give it time to stabilize itself, otherwise, you won’t get n adequate reading off the refrigerant gauges.
  4. Attach the refrigerant canister to the yellow hose gauge. Open the refrigerant canister by twisting the spout at its bottom.
  5. Now is the time to open the blue low-pressure valve on the left side. Do so for just a few seconds and then close it tightly again. Repeat several more times. You want to let small portions of refrigerant in at intervals as to not miss the desired target subcooling temperature. Watch the blue gauge to see when that happens. The temperature you want to get is the one noted on the outdoor unit’s rating plate.
  6. Once the desired temperature is reached, turn off the valve and disconnect the gauge set. Remember to twist the knob on the refrigerant canister to stop the refrigerant from going into the hose. Disconnect all hoses and gauges.
  7. Perform an electronic leak test to make sure everything is running smoothly. You don’t need to restart the AC but you do have to have the proper electronic leak detector. You can do so at most home improvement stores or online. If you don’t want to buy such tools or you don’t feel qualified to do this, call a professional instead.

And that’s about it. It’s a long process and it’s really that complicated if you know what you’re doing. However, a misstep at any stage of the process can lead to some disastrous results.

Before we end, here are a couple of other common questions we get when it comes to adding refrigerant to AC units:

How often does freon need to be added to AC units?

Never. Freon is not a consumable, it’s not meant to run out. If your AC has run out of refrigerant, the most likely explanation is that you’ve got a leak. In this case, calling a professional is your best option.

Can you add freon to a window air conditioner?

You can, the process is more or less the same as with any other type of AC. You’d do well to take the unit off its window frame to work with it properly and you’ll need to look into its technical specifics as every model is slightly different.

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