Abstract: A circuit tester for automotive electrical systems comprising a body member of "pistol-grip" configuration having an electrical socket at one end thereof and an electrically conductive probe extending from the other end thereof. An electrical lead is provided for connecting the terminals of the automobile battery to the socket. The lead has a plug at one end thereof which is reversibly receivable by the socket to enable the tester to be placed in either a positive test mode or a negative test mode. A first electrical lead member extends through the body member from the socket to the probe and has a light imposed therein. A second electrical lead extends from the socket to the probe but has a normally open, manually operated switch imposed therein. The second electrical lead member also has a replaceable fuse assembly imposed therein. The light will be illuminated when the switch is closed whether or not the probe is in electrical contact with the electrical system of the automobile or a component thereof.