i put in new alternator and new battery, but as soon as i disconnect positive terminal truck dies out? any suggestions?

why are you pulling the batt terminal ? ? ?

its another way of testing the alternator. i believe thats what i was told. i have no power. my lights on my dash keep dimming out and my radio goes off. then the next day my truck won't start and needs a jump.

Can not do that with the vehicles that have a computer you can fry the system you could do that with older vehicles to check for bad alternator. Have the changing system checked with alternator tester.

that's not how you test an alternator , no telling what else can be screwed up now , you need a multi tester and know how to use it , no biggie , I was trying to tell an engineer yesterday something simple that they could not understand then an idiot stepped in trying to help , I won't be helping them out again