Article: To recharge the refrigerant in your air conditioner, first shut down your AC unit, then follow the steps below: The low pressure hose is normally blue and is connected to the suction line—the larger of the two pipes. The high pressure hose is generally red and is connected to the liquid line, which is the smaller of the two pipes. Let it to run for at least 15 minutes so that the system can reach steady state operation. This will give you a comparative analysis of how the system is performing, with the following measurements:  The outdoor air temperature The return air temperature at the furnace/air handler The suction line temperature The liquid line temperature Newer units will usually have a label inside the electrical cover with specific instructions for your unit. It will typically tell you to measure superheat or sub-cooling. It will also give you a chart that has values for superheat or sub-cooling for a given outdoor temperature. Check the charging procedure chart in your unit to determine what type of metering device your system uses. It will either be a thermostatic expansion valve or a restrictor orifice.  If your system uses a thermostatic expansion valve (TXV), use the following values:  System superheat: 18°F (-7°C) System sub-cooling: 25°F (-4°C)   If your system uses a restrictor, you can use the table below as a guide. It contains recommended superheat values for given indoor and outdoor air temps: To find the required superheat value, draw a line from the outside air temperature down to the return air temperature. The value in that row/column is the required superheat temperature. If the tests show that refrigerant is required, check for evidence of leaks and repair them. Leaks can typically be found around any joints or connections:  Welded or brazed joints Pressure ports Threaded tubing connectors Any place where refrigerant lines may vibrate or rub against the unit chassis or other components. Do not tip the refrigerant container, as this will introduce liquid refrigerant into the suction side of the compressor, and can result in damage to the unit. Slowly, and in small amounts, introduce refrigerant into the suction line of the system, and allow 5 to 10 minutes for the system to stabilize between addition of refrigerant.  When charging a new system, or recharging an evacuated system, the refrigerant is added by weight, according to the system specifications, but trimming a unit, or adding to an existing refrigerant charge, is less precise. Check pressure and temperature readings, and determine if more refrigerant is needed. Repeat until everything looks normal. When the AC has completed a cycle, turn off power to the unit, and remove the gauges.fh

What is a summary?
Take the following steps. Attach the hoses from the gauge manifold to your system's pressure ports. Turn on the AC. Check the temperatures. Determine your metering device. Check for leaks. Connect the charging or supply hose from your manifold to the refrigerant container with the container in an upright position. Add refrigerant. Observe a complete cooling cycle.