New Serpentine belt slipping on ac compressor when engaged

[Billy177]

i have a prolblem with ac/defrost system when ever i turn on something that uses the compressor some times it will catch and sometimes it will slip and make this farting noise. i just replaced the belt with a gator back could this be just a weak tensioner or a more serious prolblem. i tried letting some of the pressure out of the ac system and that seemed to help but this still does it some times. the car has 75k on the clock

 

[mrboyle]

Its either a weak tensioner or the A/C compressor is locking up.