I am guessing that you mean the low pressure side of the AC system. Find the larger line between the compressor and where it enters the fire wall. You will find a cap for the low side. That is where refrigerant is introduced into the system.
The smaller port is the Low side port.
The low side service port is located on the suction line at the top of the engine.....
You can refill your air conditioning system from the low pressure port on the air conditioner compressor. The low pressure port will be labeled as such.
The low pressure port should be on the passenger side of the engine compartment. It is at the back right against the firewall.
The low pressure AC port can be found on the passenger side engine compartment. The port is located near the oil cap for the engine.
You can find helpfull information about your vehicles ac system including where the low side port is located on this web site www.idqusa.com just click on locate low side port.
To add Freon locate the low-pressure port on the A/C system, also called the low-side service port. You will find this port against the firewall, at the back of the engine compartment.
The low pressure side is located on the compressor. To locate the port, jack up the driver side and crawl underneath to locate the compressor. Add the freon to the port on the compressor.
To add refrigerant to your vehicle you must first locate the low side port to your ac system. There is a great web site www.idqusa.com that can help you locate the low side port on most vehicles along with helpfull information about a vehicle ac system.
On a 1992 Toyota MR2, the low pressure AC port is located on the passenger side of the engine bay. It is typically found near the firewall, connected to the AC compressor. The port is usually covered with a plastic cap, which can be removed for servicing. Make sure to identify it correctly, as there is also a high pressure port nearby.
The 1997 Toyota Avalon air conditioning low pressure switch can be found on the top of the air conditioning compressor. The low pressure switch will be labeled as the low pressure port.
The low pressure service port for the AC on a 1998 Olds Aurora is located on the side of the accumulator. It is at the back of the engine compartment, on the passenger side.