O.K, This is going to be my day for stupid questions. Where is the low side A. C. service port on the 01 K2500 HD w/Duramax? I can find the large diameter ports but not the smaller diameter low side port. Second dumb question. Where is the block heater plug in supposed to be? I have located the block heater, but lose the wire when I try to follow it over the frame rail. I just got one of those online repair manuals,but am having trouble sorting through all of the information and finding the simple stuff. Oh well, that's progress. Thanks for putting up with a newbie.