It compresses the air and supply to the air spring in order to control the vehicle level. Also it replenishes the air in the reservoir tank if necessary. It is powered by ECS relay which is located in the engine room fuse box. (rear of vehicle battery) A case is adopted covers the compressor in order to reduce the operating noise so that it cannot be separated when replace the compressor. An air filter is located on the compressor assembly as shown in the picture, it filters the dust and water whenever intakes the ambient air. It is recommended to replace every 2 years.