The evaporator is making this high pitched noise when the ac is on. I don't think it's the blower, because it only makes the noise when the a/c is on. I can turn just the air on and it doesn't make any noise. I've heard the same noise (not as high pitched though) in the plumbing in a house before in some copper pipe. Any ideas? Could it be too much or too little coolant or oil or something?