That generation is known to have noisy belt tensioner / bad idler pulley (serpentine belt runs around this) / bad belt design. The A/C not blowing cold could be an indicator of an excessively loose belt or something with the A/C clutch. Could be dragging, causing the belt to slip/jump - leading to the knocking / rattling noise.
Definitely check for noise with the belt off. If that definitely is the cause, I'd look over all the pulleys, make sure there isn't anything damaged or not turning smoothly. Double check the tensioner - if the little shock looking thing is leaking or otherwise shows physical damage - probably best to replace the whole tensioner. There are a number of aftermarket belt tensioners - I would also try running something like a Gatorback Poly-cog or similar replacement belt. Way better than the OEM Bando belt.