A/C Problem

for those who have more experience working on chevys then i do, my my ac stopped working in my trailblazer. Whats happening is, when the system is charged, everytime you turn on the A/C or the defrosters, when the clutch for the compressor turns on, the truck trys to bog down to were it pretty much stalls out. I replaced the A/C compressor thinking it was bad, and it still does the same thing. Heres what gets me though, when u discharge all the fluid out it doesnt try to bog, because u used the defrosters all winter and had no problem, but as soon as i went to recharge it it trys to bog. I talked to a few people about it and one guy suggested a clogged line and to go to get the backpressure checked to see if thats it? any other ideas? trying to do the most i can before i take it in for a service.

 

i'm guessing something's clogged...but i really have no idea. might be in the wrong forum too