Any AC system requires a refrigerant, such as R-134a. Your vehicle’s compressor, powered by the serpentine belt, compresses the refrigerant into a liquid, putting it into a high-pressure state. This pressure forces the liquid out of the compressor through the hoses in your AC hose assembly, which carry refrigerant through the system. Regardless of which of the systems your truck uses, the compressed refrigerant travels from the compressor to the condenser on the high-pressure side of the system to cool off before reaching the AC evaporator core on the low-pressure side.