Description Auto Lock feature will AUTOMATICALLY LOCK UP fan clutches when the friction material nears the end of its life, allowing the vehicle to finish its trip. Application Peterbilt / Caterpillar C15 *There is a $250 core charge. Cores can be returned for a $250 refund. Fill out and print the form below and add it to the return box, send cores to: SP Truck Parts Core Return 30026 Beverly Rd Romulus MI 48174   Fan Clutch Core Return Form