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Re-Charge an Air Conditioner System

Air Conditioner Recharge Gauge

How to Re-Charge an Air Conditioner System

To charge your car's air conditioner you will need a set of gauges to hook up to both the high and low pressure ports of the air conditioning system. Uncover the ports and attach gauges to take a reading of your low and high pressures values, you always want to stay within manufacturers recommended values. The compressor pressurizes the refrigerant gas which gets very hot in the process and circulates it through the condenser (small radiator for heat dissipation, located in front of the radiator) mounted in the front of the car usually behind the engine radiator to cool the hot gas. 

As the gas cools when leaving the condenser it becomes a very cold liquid and enters the evaporator (another small radiator) that allows the air inside the passenger cabin to be cooled as it is force through the very cold fins of the evaporator. The entire air conditioner system is under pressure and should not be worked on carelessly. If you are planning on recycling your refrigerant you will need a recovery tank as well. Normally the entire system will hold over 2 pounds of refrigerant, you may not need very much to make your air cold again. If the car engine is overheating the air conditioner will not work because there is no heat transfer through the condenser.

Most air conditioners will shut off if there is not sufficient refrigerant in the system and that can be as little as one half pound light. You can have 1.5 pounds of refrigerant in a system that is full at 2.2 pounds and it acts like it is empty. When adding refrigerant, only fill using the low pressure port and fill in small increments. Run the air conditioner on max while the radiator is being sprayed with water to simulate driving conditions and so the engine won’t overheat. When the air gets cold coming out of the vents you have enough refrigerant, you don’t want to over fill the system, there is not extra room for the gas and that can damage the compressor. The air conditioner lines leaving the compressor should be hot and the lines entering the evaporator should be very cold. Monitor the pressure levels when filling the system, using caution to avoid a run up of pressure. Put caps back on the ports and enjoy your comfortable passenger cabin once again.


Before getting started with charging your air conditioning system lets take a look at what we have to work with. Please visit: How an Air Conditioner Works.

Park your car on a level surface with the engine warm but not running. Apply the emergency brake and put the transmission in park. Wear protective clothing, gloves and eyewear.

If you are not sure about why your air conditioner is not working please visit: Air Conditioner Not Working.


Tools and Supplies Needed to Complete this Job

1. Air conditioner recharge gauge set

2. 134a Refrigerant

3. Small pliers


Instructions

Step 1 - Locate high and low side pressure ports, the low side is usually located in the suction or larger diameter hose from the firewall to the rear of the compressor. The high pressure port is located on the smaller diameter hose between the compressor and the condenser. (Note: never try to charge an air conditioner system through the high side port.)

Step 2 - Remove the dust cap from the low side port and attach the re-charge gauge.

Step 3 - Start the engine and turn the air conditioner to the highest high speed and coldness setting.

Step 4 - You might hear the compressor clicking on and off, this is normal most of the time when the system is low on charge.

Step 5 - Attach the charge gauge to the low side pressure port.

Step 6 - Open the valve to allow the 134a to flow into he low side port. Have a helper monitor the temperature of the air being produced from the vent. Stop adding when the air is cold. (Note: never overfill the air conditioner system)

Step 7 - Turn the engine off and disconnect the gauge fill hose and re-install the dust cap. (Note: if the system remains cold for a period of time and once again stops working the system has a leak and repairs must be performed.)


Best Practices

  • Clean evaporator at the front of the vehicle to ensure maximum system performance. You can use a garden hose or compressed air to clean the cooling fins.
  • If you have charged the system but it still doesn't get cold the system has an internal problem and repair will need to be made. These problems include: failed compressor, expansion valve, orifice tube or cooling fan motor.

If further technical assistance is needed, our certified car repair technicians are ready to answer your car questions.

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