98 Aurora AC Charging

I'm wanting to check and charge my Air conditioner system but i can't find the low side connector. The high side has 2 different connectors but i don't see the low side connector. Can anyone give me directions to where this fitting is. You would think they would make it visible and easy to get to, but i guess nothing is simple anymore. Thanks for any help you can give me, Randy

low is closest to firewall