How to Check and Refill Refrigerant
Checking and refilling the refrigerant in your car's air conditioning system is not a difficult task. However, it can be a dangerous one if you do not have at least a little understanding about how the system operates. You also need a gauge to tell you when the system is fully charged. The gauge will keep you from having a can of refrigerant explode in your hand or in your face.
The air conditioning system on cars runs with a great deal of internal pressure. The job of the compressor is to boost the pressure in the high pressure side of the system. When the refrigerant hits the spot where evaporation occurs, it generates enough evaporation by reducing the pressure to create the cool that keeps your car comfortable in hot weather.
After the evaporation happens, the coolant travels though the other half of the system called the low pressure side as it returns to the compressor. It is important to be able to identify the high and low pressure sides of the system because both have valves in the line. However, the can of refrigerant is designed to only handle the pressure of the low pressure side. If you attach it to the high pressure valve, it can explode.
The good news is that on most cars, the high pressure line is clearly marked. If you have any doubts, do not attempt to recharge the system until you can definitely tell which is the low pressure line. Once you have identified the correct line, attach the line with the gauge to it. On most gauges that are sold at discount stores and auto parts stores are markings that indicate if the system is running low on refrigerant based on the line pressure. A green shaded area gives the normal range and a red zone indicates that the system is running too high.
Do not add refrigerant to a system that indicates that the pressure is too high. It is best to take that problem to a professional rather than risk injury to yourself or damage to your air conditioner. If the gauge shows that the pressure is below or at the very low end of the normal range, you should be able to recharge your system.
Follow the directions that came with the gauge and refill hose for attaching the can of refrigerant. Usually, the can latches to the fitting on the end of the hose opposite the quick change that attaches to your air conditioning system's low pressure line. Once the can is latched in place, you can screw down the pin that pierces the top of the can to release the refrigerant. This device also acts as the valve.
Turn your air conditioner on to maximum cool. Once the can is pierced, unscrew the valve to begin releasing the refrigerant into the line. Turn the can upside down to let the liquid flow from the can into the air conditioning system. You will want to rotate the can from upside down to upright. This will keep you from overloading the system with liquid. Shaking the can will help the refrigerant to keep flowing evenly into the line.
If the refrigerant is leaving the can, the can will get very cold. It may even start to form ice on the outside of the can. This is normal and means that your system is accepting the refrigerant. You will feel the can get lighter as it empties. When all of the refrigerant has left the can, it will begin to return to air temperature.
You can feel the refrigerant shake in the can. When it no longer has any liquid, it is time to disconnect it and throw it away. If the gauge still shows that your system is low, you can add a second can. For most systems, one or two cans will usually change them from warm to cold.
When the gauge reaches the middle to upper half of the normal range, the system should be charged. Leave refrigerant in the can rather than overcharge the system. Check the amount of cooling coming from your vents. If it feels like it is cold, you have probably put in enough regardless of what the gauge shows.
If you have to recharge your system more than twice per year, you probably need to take it to a shop and have the leak repaired. Most of the time, one recharge will carry you through the entire summer and maybe longer.
