1999 Honda Civic A/C compressor

Air Conditioning problem
1999 Honda Civic 4 cyl 155, 00 miles

I recently put a lot of money into fixing my car lately. I put in a catalytic convertor, O2 sensor, water pump, new timing belt plus a bunch of other problems. I does have a oil leak that hasn't be repaired but I was told it's an emergency. Now 2 weeks after my repairs my AC shuts off and I brought it to a mechanic and he said I need a new AC compressor. I declined since it's a $900 repair. But now when I drive my car it makes a horrible grinding noises when my AC button is off and when starting and shutting off the engine. Is the compressor making that noise or is something else wrong with this automobile?