Where is the r134 port location to recharge A/C refrigerant on 1998 GMC Sierra or...

[lostcaliforniakid]

...Silverado? I know I am looking for the low side r134 port (1998 should be a 134 system). Things I have read say the cap should be blue or black and have an "L" on it... but I can't find this. About in the middle of the engine is what I believe to be the a/c compressor and it has two ports, but no informative markings on the caps (one port face up, the other faces to the front towards the radiator). Help, where is the low side r134 port?!

 

[Ronnie]

The low side port is the smaller of the two.