AC systems work based on condensing a gas to a liquid, then heating that liquid back to a gas. The main heart of the AC system is the compressor and condenser. The compressor creates a high pressure gas which is “condensed” to a liquid. The fluid is pumped to the evaporator where before entering, the liquid Freon goes through a metering device. This device simply causes a large pressure drop in the liquid. This pressure drop causes the Freon to remain a liquid but is very cold. As the cold Freon moves through the evaporator it absorbs heat from the house air. The Freon continues to absorb heat unit it boils to a gas or “evaporates.” The gas is then returned back to the compressor where the process repeats.