Aftercoolers install on the air compressor, or immediately downstream, to cool the hot compressed air. As hot air enters the aftercooler, it travels through a coil system. Fan-powered aftercoolers cool the air with a motor-driven fan that blows air on the coils. Belt-guard-mounted aftercoolers attach to the compressor's v-belt guard where the air from the pulley system forces air over the aftercooler's coils.