you may have a clogged condenser if the car has ever had an ac compressor seize small metal fragment build up into the condenser causing it to restrict air flow through the system or the magnet that engages the clutch could be going bad and could not be getting the constant 12v power it needs to keep the driven wheel engaged so i would try to take apart just the pulley and clean each part the best you can and reassemble it also ad just a little grease to the inside of the bearing to ensure that no grinding from dust or dirt causes damage you can also clean the bearing with Isopropyl alcohol to remove all dirt and dust then re grease after it is completely dry hence Isopropyl alcohol dries the fastest if that does not work check for leaks in the system if no leaks make sure your getting a constant 12v power to the plug be sure to check your fuse panel for the ac relay to make sure that the relay is good other than that if none of these fixes work it is going to be a problem inside of your ac compressor and at that point it will be cheaper to get a new one because having someone rebuild the insides of your compressor is expensive and a hassle so i hope this helps you fix your problem good luck man
