Watch this "Grease On Your Hands" video tutorial from the Washington Post to see how to check and charge car air conditioner properly.
When servicing any automobile, you should always wear appropriate eye-protection as well as ensure your working environment is properly ventilated. When working underneath a vehicle, always secure it with a floor jack and jack stands or drive-on lift ramps. You're going to get greasy as well so keep a healthy supply of rags on hand to sop up the mess!
Necessary Materials: A/C System Meter and R-134a Refrigerant & Oil Combo Canister (if your vehicle uses R-12, you will need to take it in to a service center since R-12 is not available for public consumption, due to its overly detrimental effects on the environment)
Instructions and Tips:
1. Turn on the Vehicle and switch on your A/C settings to maximum cold.
2. Locate your Low Pressure A/C spigot, located on the A/C line feeding directly into the A/C compressor (the unit with the belt on it). The spigot should be labeled with an "L" or "Low". Do not use the High Pressure hose, it will likely damage your meter and might even cause damage to the entire system.
3. Attach the meter onto the "Low" line spigot and determine if you need additional coolant.
4. If so, screw the canister onto the fitting of the meter/changer and add in refrigerant, constantly monitoring the pressure level to ensure that you do not overfill! You can seriously damage your system by overfilling.
5. After fully recharging the system, make note of the pressure level and recheck this in about a week to ensure your system contains no leaks. If you realize diminished cooling power or a loss in pressure, you probably have a leak. Please allow a professional to service the system, sealing up any leaks you might be experiencing.