There is no way to turn on a car’s radiator, but there is a computer-controlled fan that can be turned on and off. Find out which relay controls a radiator fan by checking the fuse box with help from an ASE-certified mechanic in this free video on understanding auto parts. Expert: Tom Brintzenhofe Bio: Tom Brintzenhofe has been a mechanic for more than 17 years. Filmmaker: Reel Media LLC