An easy way to understand the purpose of refrigerant in your air conditioner is by comparing it to blood in the body. The refrigerant flows through the AC system, changing from a gaseous state to a liquid state, and leaves your home nice and cool as a result. Without the perfect amount, the system (or body) will fail to operate properly. However, this phase change is impossible without the compressor, the component that pumps the refrigerant through the system. In this analogy, then, the compressor is the heart. Likewise, a broken compressor won’t be cheap to fix. Before it gets to the point that you need to call an AC repair service, you can first look out for the symptoms of compressor failure as explained in the causes below.