If you are talking about the low side for the AC system. there should be 2 ports. The port that is on the largest diameter line is the low side.
The 2002 Chevy Cavalier low side service port can be found on the top of the air conditioner compressor. The low side service port will be labeled as the low pressure port.
You can find the low side air-conditioner import on the top of your 1986 Chevy Caprice air conditioning compressor. The low side air-conditioner port will have a blue top.
The AC low side service port on a 1999 Chevy Astro van is located next to the firewall. It is the port that is closest to the evaporator.
The recharge port is on the larger AC pipe
On the accumulator.
The 2001 Chevrolet Impala low side service port can be found on the top of the air conditioner compressor. The port will be labeled as the low pressure port.
To the fuel tank
Low side service port is against the firewall just underneath the alternator. It has a Blue cap on it.
The low pressure service port on your Chevrolet K 1500 air conditioning compressor will be the one closest to the front of the engine compartment. The low pressure service port should be labeled.
Into the low side service port.
In the low pressure service port, the smaller of the two.
Reach down between the alternator pulley and the firewall. The service port is down there. has a blue plastic cap on it.