How to Add Refrigerant to an A/C Unit

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By Nathaniel Miller
eHow Contributing Writer

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One of the optional pieces of equipment for your car is an air-conditioning unit. This unit cools the outside air as it enters your engine compartment, then pumps that cooler air into the cockpit of your car. Over time or because of small leaks, the refrigerant in your car's A/C unit may need replaced. It is fairly easy to add refrigerant with the proper equipment and know-how.

Difficulty: Moderate

Instructions

Things You'll Need:

Set of refrigerant gauges
Puncture frame to fit gauge
Can of refrigerant

Step 1

Start the car and turn the air conditioner on full blast. Raise the hood to inspect the A/C compressor clutch for operation. Check the condenser fan; it should be blowing air across the condenser coil, which is near the radiator coil.
Step 2

Shut off the engine, and connect the gauges to the fittings on the A/C compressor. Check the pressure with the engine off. Normal system pressure should be around 125 psi; if the gauges read below this, then the system is low on refrigerant.
Step 3

Start the engine and let it run for a few minutes.
Step 4

Screw the hose fitting onto the compressor fitting, and install the can of refrigerant into the puncture frame. Screw the fitting down to puncture the can and allow the refrigerant to enter the AC system. When the can is empty, unscrew the fittings from the compressor.

Tips & Warnings

Do not charge your A/C unit over 150 psi, as this could overcharge the unit, which will prevent proper cooling. A range of 135 to 145 psi is good enough for most A/C systems.