Can I recharge my window unit air conditioner or do I have to send it to a specialist?

The AC unit that I have is about 15 years old (nothing lasts forever)... and I happen to have about 20 lbs of R22 on hand... so I wrote this up. The AC isn't really leaking, but after about 15 years I have lost a couple pounds.

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  • 3
    You might want to repair the freon leak first. The freon wasn't beamed out by Geordi LaForge. For the vast majority of window unit air conditioners, you can buy a new one cheaper. And then the energy savings from the more-efficient new ones will pay you further dividends. Commented Jun 17, 2016 at 23:22
  • 2
    In all my years I have seen but one window unit with a schrader valve on it. I threw it away anyway, because: NO ONE DOES THIS.
    – Mazura
    Commented Jun 18, 2016 at 1:15
  • They're sealed systems for a reason. If you've lost freon, it's because you have a fracture in the tubing that will quickly leak out what you put in. @Mazura - exactly, the Shrader valve is a designed in leak. Poor design as all the wall unit AC and refrigerators I ever worked on had exactly the same amount of freon they left the factory with, unless someone defrosted them with an icepick or did other system breaching damage. Commented Jun 18, 2016 at 6:31

3 Answers 3


It's a waste of money to try. Especially if you're the guy who pays for the electricity.

Captain Kirk didn't beam the Freon out.

First, you'll want to fix your Freon leak. After all, air conditioners are generally sealed units, with only electrical wires entering the envelope that contains freon. However, they use a lot of aluminum, as it is a superb themal conductor, and cheap. Accumulated dust in the cooling coils and fins tends to hold water, a perfect storm for aluminum corrosion. Good chance you have a pinhole in the condenser.

Likely you have a foreign made pile of junko, so there is nothing in the unit designed to help you. Every inch of tubing in the unit is welded, and there are no spare parts to be had for the mechanical package. (Control board, yes.)

If you have an old school solid American unit, it most likely takes the long-discontinued R12 or R22 Freon, so you are paying top dollar for old stocks.

Refilling is dangerous

Contrary to what comic books say, a Freon accident will not turn you into Mr. Freeze. Cold is not like fire, you don't instantly feel the pain, you can expose yourself long enough to do damage before you realize it.

And there you are, using third party parts of dubious quality, since no manufacturer endorses even authorized repair of the Freon containing machinery - it is not economical even if they made it easy, which is why they don't.

Who pays the electricity bill?

If it's you, you're paying again to run an old inefficient unit. Ten years ago I bought a solid Sears unit that did 5600 BTU and drew 5 amps. My friend just bought a private label no-brand junko unit that did 8000 BTU for 5 amps. His unit runs 1/3 less often, so he's saving about 200W or 1 KWH every 5 hours. An older unit would be even worse. This is due to Federal laws requiring ever-increasing efficiency. Do the math... Then imagine what a quality unit would do.

Even if you can get 5 more years out of your old unit, the new unit will pay for itself in electricity costs alone, to say nothing of all that other stuff.

So fixing an old unit is a false economy.


Air conditioners do not magically lose refrigerant.

If refrigerant is missing, the air-conditioner leaks; if the leak is not fixed, it will continue to leak.

A window unit is almost always a bad economic choice to attempt repairs on rather than replacement; since USA-based persons DO need a license to handle refrigerants, and anyone world-wide needs specialized equipment (and one, hopes, enough training to use it correctly), the cost of service (particularly with older, very expensive refrigerants) is far above replacement, particularly when the power efficiency of a newer unit when running is factored into the equation.

The cost of having a qualified, equipped person (or becoming that person) find and repair the leak (on a unit typically not made with ease of service and repair in mind) will almost always exceed the cost of a new unit to replace it.


What you need to know:

You are supposed to be EPA certified to work with freon, so the following is only for educational purposes and some pertinent information may be missing.

An air conditioner should be cooling the air by about 15 to 20 degrees Fahrenheit. To check that, hold a thermometer in front of the air conditioner where the air is comming out. It should be about 15 to 20 degrees cooler than the temperature of the air in the room (more specifically, 15 to 20 degrees less than the air going into the air conditioner).

Window units prior to 2010 primarily use(d) R22 (also called HCFC-22) freon. R410A (also called Puron) is the standard as of 2015. A 5 ton AC unit has 10 to 20 pounds and a 3 ton AC unit has about 6 to 12 pounds of freon. What do I mean by tons? Tons are kind of like horse power. Tons refers to the amount of ice that would be used to remove a similar amount of heat (and for window AC units, it's around 3 to 5 tons per hour).

R22 systems use mineral oil for lubrication whereas R410A uses a synthetic polyolester oil. Mixing refrigerants is illegal in USA.

Most window units do not have a port installed so that you can add freon.

The larger copper tube leading to the compressor is the low presure side (and the smaller tube is the high pressure side).

Generally, about 1 or 2 pounds of refrigerant should be enough to top off one AC unit. How do you measure that? One way is to put the canister of refrigerant on a bathroom scale and weigh it... a bathroom scale might not be perfect, but it should be pretty close.

You probably won't need to add more oil.

What you need:

  1. EPA certification.

  2. A self piercing valve (currently the price is about $2 to $5) to the low pressure copper tube. The tubing size may be 1/4", 5/16" or 3/8" so you will need to measure that first or get a "universal" piercing valve that accomodates multiple sizes.

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  1. A refrigerant refill hose (currently the price is about $10 to $30).

  2. Refrigerant: currently the price for R22 is about $260 for 10 lbs and the price will continue to climb until the stocks are depleted; or for R410A refrigerant, the price is currently about $110 for 25 lbs or you can get about 28 oz for about $70.

What you need to do:

Measure the temperature to see if you need refrigerant. Check the make and model of the air conditioner to find out if you need R22 or R410A. If you need R22 the cheapest option would be to replace the window unit. Measure the size of the low pressure tube and order a self piercing valve. Order the refrigerant and any necessary hoses or connectors. Attach the self piercing valve to the most convenient/accessible location along the low pressure tubing. Turn on the AC unit (max-high) and add the refrigerant while it is running (warning!!! watch out for exposed electrical wires). Don't forget the bathroom scale, to weigh the canister (before and after).

Here's a few youtube videos with some extra info:

How To Install Bullet Piercing Valves To Charge Refrigerators Or Air Conditioners Low On Freon

Duracool 22a Recharging Kit

Helpful Tip: Air Conditioner Repair | Adding R-410A Refrigerant to a System | NORDYNE U

  • 2
    I own most of the equipment to do this with, but I never would (then again I horde old window units in my basement, so that I can lend, abuse, or toss-and-replace them at will) because "Most window units do not have a port installed so that you can add freon." Most 'broken' window units that I find laying around or tossed out, simply needed to be hosed off, or their corded-GFCI replaced. Once a window unit leaks, it's done IMO. That +$100 in materials could just buy you a used working unit.
    – Mazura
    Commented Jun 17, 2016 at 21:31
  • Even the newer window 134a units have a problem when the condensing / outside coil is plugged and they over heat I have not had much luck pulling a high vacuum reclaiming what was in the system and recharging. Sometimes they do work but many times only marginally so it may be cheaper to get a new unit and keep the condenser coil (outside) clean and the inside filter elements cleaned than try to fix a old unit.
    – Ed Beal
    Commented Jun 17, 2016 at 23:43
  • @EdBeal I didn't know that 134a was used in anything but vehicles. Commented Jun 19, 2016 at 16:43
  • It is used in window AC units ,air dryers and refrigerators that I know of and have serviced, my supplier can get the R134A with the acme thread for vehicles 30-50$ cheaper than the exact same thing with standard fittings. So I got the acme adapter and have saved several hundred over the years (608 universal & 609 MVAC certified)
    – Ed Beal
    Commented Jun 19, 2016 at 17:29

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