A Mustang A/C condenser works by placing freon gas in a sealed system. The freon is then pressurized using a compressor. As it's pressurized, it gets hot by absorbing the heat around it. This hot gas is then circulated through the A/C condenser, which is simply a series of tubes that dissipate the heat by allowing cool air to flow around them. The freon gas can lose lots of heat (get cold) when you reduce the pressure, then as it cools it becomes a liquid.