Number 16 is your low side connection is this the one that you are on?
ok what is the high side reading by chance?
#3- receiver dyer
7- a/c pressure switch or high pressure switch
12- expansion valve or H-block
16- low side connection
18- high side connection
20- evaporator located in heater box in the dash
33- pressure relief valve
34- ac clutch
your normal ac low pressure should be around 22-36 psi within 30secs of turning on
your normal high side pressure should be around 232 psi within 30 secs of turning on