The A/C compressor on a 2001 Ford Focus is typically located on the front of the engine, driven by a serpentine belt. However,
you do NOT add refrigerant (coolant) directly to the AC compressor. Adding refrigerant requires specialized equipment to measure the system's charge and prevent damage. Attempting to add refrigerant without the proper equipment can be dangerous and may further damage your A/C system.
To service your A/C system (which includes adding refrigerant), you should take your 2001 Ford Focus to a qualified automotive repair shop or a shop specializing in air conditioning repair. They have the necessary tools and expertise to diagnose the problem and add the correct amount of refrigerant.