A simple tester (J 34764) can detect a blown fuse. To check a fuse, the tester is applied directly to the fuse in the Fuse Block. Two probes contact the fuse, either into the slots of a flat fuse or to the metal ends of a glass fuse. With power ON, a red Light Emitting Diode (LED) in the tester lights if the fuse is open. The handle of the tester is a tool for removing either type of fuse.