How To Recharge Your Air Conditioner with Freon

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Can You Recharge Your AC With Freon?

Recharge your air conditioning with new R134 refrigerant, freon.
If your car uses R134 type refrigerant, you can recharge your own AC system. photo by Matt Wright, 2008

Before you set out to recharge your car's air conditioning system, you need to be sure your car uses the newer R134 (not the older R12 refrigerant). The best way to determine this is to check your car's owners manual, or you can consult your repair manual. You do have a repair manual, don't you? It's a must for do-it-yourself auto repair.

If your car was manufactured after 1994, chances are you're in the R134 camp. If your car uses the older R12 refrigerant, you should take it to a repair shop and have it converted to the newer stuff so you can be in the cool again.

If your AC system is R134 equipped, read on and we'll help you recharge your air conditioning so you'll be away from the "blowing warm" blues.

*If you have refilled your AC system before, and find yourself needing a recharge again today, you might want to check it for leaks. For a primer on the air conditioning system itself, check out How Does My AC Work.

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The AC Recharge R134 Kit

How to charge car air conditioner.
An R134 recharge kit includes a pressurized can of refrigerant and a pressure gauge. photo by Matt Wright, 2008

To recharge your air conditioning system you'll need pressurized refrigerant (sometimes referred to as freon) and a pressure gauge to keep track of how much is in the system. There are lots of different AC recharge tools you can buy, but most are for the professional and are pretty expensive. If you have a fleet of vehicles you plan to maintain, go ahead and spring for your the real deal, but if you're air conditioning maintenance is limited to a couple of family cars, I suggest one of the all-in-one kits. These kits consist of a can of R134 and a pressure gauge all in one. They work well and are very easy to understand, even for somebody who has no experience with AC.

The kit we chose had the pressure gauge clearly visible in the cap, so you know what you're getting. Any all-in-one kit is probably fine.

You might also want to check for leaks in your system to be sure it's healthy.

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Preparing the Recharge Kit

Back the gauge out so you don't pierce the can too soon.
turn the gauge counterclockwise to retract the pin that pierces the can. photo by Matt Wright, 2008

As you unpack your kit, you'll find a can of refrigerant, a flexible rubber hose and a pressure gauge. Follow the instructions in the package to assemble the pressure gauge part of the kit. Usually you'll have the hose already attached to the gauge. Before you screw the gauge into the can of refrigerant, be sure to turn the gauge counterclockwise until it stops. There is a pin inside the assembly that pierces the can of refrigerant once everything is together tightly. This pin is controlled by turning the gauge clockwise until it pierces the can. But you don't want to do this until you're ready, so be sure to back it all the way out before you assemble everything.

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Assembling the Recharge Kit

Assembling the AC pressure gauge.
Attach the hose to the pressure gauge. photo by Matt Wright, 2008

With the piercing pin safely retracted, you can assemble the pressure gauge and the kit. Screw the rubber hose onto the pressure gauge and tighten it. You don't need to screw the whole thing onto the top of the can yet, we have something to check first.

Now's also a good time to calibrate the gauge. This is a basic procedure. On the face of the gauge you'll see different temperatures. All you need to do is turn the calibration dial to the outside temperature (how hot is it today?). Also be sure your coolant is topped off as your Ac system adds heat!

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Locating Your Low Pressure Port

Use the low (not high) pressure port.
Locate the low pressure port, that's where your action will be. photo by Matt Wright, 2008

Your air conditioning system has two "sides" -- a low pressure and a high pressure side, depending on where you are in relation to the compressor. You'll be recharging your AC through the low pressure port. You should consult your owner's manual to be sure, but your vehicle will have a cap over the pressure ports. One cap is labeled "H" (for high pressure) and the other is labeled "L" for low. As a further safety measure, the ports are different sizes so you physically cannot attach the pressure gauge or hose to the wrong port! It's pretty failsafe, but always double check yourself to be sure.

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Clean the Low Pressure Port

Cleaning the port.
Carefully clean the low pressure port. photo by Matt Wright, 2008

Your air conditioning system has a fragile side. If any debris gets into the compressor it can cause it to fail prematurely, and this can be expensive. To be safe, you should clean the outside of the low pressure port before you remove the cap, and then again after the cap is removed. This may seem like overkill, but one grain of sand can ruin a compressor.

For more info on your AC system, check out How Your AC System Works, you'll be way ahead of the game when it comes to repairs.

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Attaching the Hose and Testing the Pressure

Attach the gauge hose to the port.
Pull the sleeve back and slide the fitting onto the low pressure port. photo by Matt Wright, 2008

IMPORTANT: Before you attach the hose, you'll need to turn the gauge clockwise until it stops tightly. This will seal the gauge off so you can safely attach it to the AC port.

With the port cleaned, you're ready to attach the rubber hose that links the car to the pressure gauge. they don't screw on, but instead use a quick and simple latching mechanism. Too attach the hose to the low pressure port, pull the outside of the fitting back, slide it over the low pressure port, then release it.

Now start the engine and turn the air conditioning on high. Take a look at the gauge and you'll see how much pressure your system is building. Give it a few minutes to get the pressure up and equalize, then you can take an accurate reading to see how badly (or not) you need to recharge the AC system.

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Preparing to Add Some Refrigerant

Now you can pierce the can of refrigerant.
Turn the gauge clockwise to pierce the can. photo by Matt Wright, 2008

So you need to add some R134 refrigerant to the system to get the pressure up? No problem. Remove the hose from the port.

Turn the gauge counterclockwise again to retract the piercing pin.

Screw the pressure gauge assembly onto the can of refrigerant tightly. Finally you get to pierce the can! Turn the gauge clockwise all the way, and you will hear the pressurized can pierce.

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Adding the Refrigerant to the AC System

Rotate the can back and forth as you fill.
As you add refrigerant, rotate the can back and forth. photo by Matt Wright, 2008

With the can pierced, reattach the rubber hose to the low pressure port on the AC line. Start the engine and turn the AC onto high. Give the system a minute to pressure up, then turn the gauge counterclockwise to start releasing the R134 into the system. Watch the pressure gauge as you add refrigerant. The area of the gauge that corresponds to the outside temperature will tell you when the system is full. You can find more information in the instructions that came with the all-in-one recharge kit. As you add refrigerant and wait for the pressure to come up, slowly rotate the can back and forth to distribute the good stuff as it comes out.

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Wrapping It Up

Reading the gauge.
This system reads a low 10 pounds, so keep adding. photo by Matt Wright, 2008

Keep an eye on the gauge as you fill and you'll get the right amount of refrigerant in. Don't worry if you are off by a few pounds, it's not a big deal. The gauge in the above photo only reads 10 pounds, so this system was very low on refrigerant. Fill it to the proper level and you'll have cold AC once again.

When you're finished filling, don't forget to put the cap back on the low pressure port to keep gunk out. Even if the can is empty, hold on to the pressure gauge because not only can it be used to check your AC system pressure, next time you add refrigerant you will only have to buy the can!