While your AC unit will make some noise, it shouldn’t be too loud. You’ll hear the fan turn on when your AC unit is triggered, and the compressor will make some noise. However, you should be wary of banging, buzzing, hissing, clicking, and screeching noises — these are all indications that something is wrong with your AC unit. For instance, you may have a leaky refrigerant line, which can cause it to hiss. Or, you may hear a clicking noise which can be caused if your fan is off-centered.