Air Conditioner making knocking and wobbly, unstable noise.

Hello. I have a Haier window air conditioner unit, an energy star series. Model number ESA306. When it’s running on high it is pretty loud and makes a wobbly fan or weird fan bearing type noise that makes it sound like something it just out of place. Almost sounds like a “chugging” noise with occasional vibration of something inside. On medium it sounds about the same but a tad quieter, and on low it makes a loud knocking noise like the fan is about to fall off. I just picked up this air conditioner to see if it worked, I found it in the lobby of my apartment- someone was going to throw it out. It blows cold air and the thermostat is accurate, but that loud fan noise is just too much. Any ideas?