How to Add Freon to an Air Conditioning Unit

Automotive freon is contained within the air conditioning system for cooling the interior. With a condenser and evaporator, the air is run through heat-finned coils that cycle freon. The designation "R-134a" is the current replacement for "R-12", which was phased out due to atmospheric pollution. Commonly referred to as "134a", it is often vacuumed into the system at a standardized nipple with a small amount of lubrication. The average backyard mechanic can add freon to an empty A/C system in about 20 minutes.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• R-134a refill kit or R-134a to R-12 replacement conversion kit
• Lock grip pliers

Adding freon to an automobile

1. Empty and evacuate the system. Old lubrication or contaminants could damage the system unless removed. Most automobile repair shops will evacuate the old freon for free, as they get reimbursed for collecting it. This is especially important if the system is being converted from R-12, as the two freon types do not mix.

2. Locate the freon nipples on the condenser. The condenser is a large silver canister, usually located on the left side of the engine. The A/C system will have two nipples, and they are different sizes. They should be color coded, but since they only attach to the correct hose tip they might not have coloring.

3. Connect the filling hose (gauge optional) to the can of freon. It will twist on clockwise, and puncture the can once seated. The hose will have a valve or trigger, and this should remain closed until connected to the vehicle. There will be an audible hiss when the can has been punctured by the hose's screw clamp.

4. Connect the other end of the hose to the condenser at the appropriate nipple. It will push on, and lock when seated.

5. Crank the vehicle, and let it idle with the A/C turned on. Be sure there are not any obstructions in the engine bay.

6. Twist the valve on the freon hose, and let the can empty into the condenser. Do not shake the can, or turn it upside down. With the A/C on its maximum setting, the system should consume a 10-ounce can in about three or four minutes.

7. Replace the can with a can of lubricant, and let the condenser consume it. When the freon can is empty, it will be very light. Close the valve, then slowly unscrew the can from the hose clamp. It may hiss slightly from the air pressure differential, but should not spew freon. Screw on the lubricant (sometimes added to freon), and let the system vacuum it in.

8. Repeat the procedure until the system has been filled with the correct amount of freon and lubricant. This amount can be found in the maintenance specifications for the vehicle, but typically a system will take about two cans of freon and one can of lube.

Tips & Warnings

• Using a 2-to-1 ratio for freon to lube is common.
• Do not add R-134a to an R-12 system without removing the R-12, as this will damage the system. A conversion kit will come with nipple adapters that will allow the R-134a hose to attach to an R-12 system.