Problem with A/C on 2000 Suburban

[Lost-Bunch]

I have a 2000 Suburban that the A/C is driving me crazy. Last year I replaced the belt tensioner three times, last one was from GM dealership. They are over extending and coming in contact with the A/C compressor. The front A/C works great, very cold, the back however does not work. Checked in the back panel and the flapper is directing the airflow correctly, so I guess there is no freon getting to the back. Had gauges put on while the tensioner was contacting the A/C pulley and pressures looked right on. My question is, do I need an all new A/C system or could it be just a clogged orifice going to back causing over pressurization of the system ??? Thanks for any thoughts you may have. I would rather not have to replace the hole system (compressor, dryer,) if i don't have to.