I ended up scouting around in the dark last night and I couldn't find the low pressure ac port on my 02 f150. 4.6l

I just bought the vehicle and the ac doesn't get very cold. I have a set of guages and wanted to check it, but couldn't find the thing.
any hints?????!!

 

#5 is the Low side and #2 is the High side:

 

thanks, that's a huge help.