my brother and i just changed my water pump, timing belt, serpentine, and tensioner not too long ago, and just recently i bought r134a to put in my car. after i added the r134a, whenever the compressor kicks on, it chirps the belt at idle. i asked one of the dudes my brother works with that does a/c all the time, and he said the compressor (not the clutch) is on the way out. my a/c system had very little pressure, so i think a previous owner just vented it off to keep the belt from squealing, or maybe i need a shot of oil, but my brother told me i should never need to add oil to a working system.
