Abstract: Apparatus is disclosed for preventing theft or unauthorized use of motor vehicles. An auxiliary electrical switch is mounted on the housing of the ignition or starter key cylinder, and is connected to a fuse in the main electrical circuit. When the key cylinder is removed and the ignition or starter switch is shorted, this auxiliary switch causes the fuse to blow out and disable the electrical system in the vehicle. The ignition or starter switch actuates a relay, which in turn is connected to a valve mechanism in the fuel line and the ignition coil or starter through independent circuits. Actuation of the relay causes electrical power to be delivered to the fuel valve and ignition coil or starter. When the relay is de-actuated, the ignition coil is grounded, and the vehicle cannot be started with a jumper wire. A further switch is disclosed for disabling the relay.

Abstract: Electric disabling circuits and components are provided for preventing theft or unauthorized use of motor vehicles. An auxiliary electrical switch is mounted on the housing of the ignition or starter key cylinder, and is connected to a fuse in the main electrical circuit. When the key cylinder is removed and the ignition or starter switch is shorted, this auxiliary switch causes the fuse to blow out and disable the electrical system in the vehicle. The ignition or starter switch actuates a relay, which in turn is connected to a valve mechanism in the fuel line and the ignition coil or starter through independent circuits. Actuation of the relay causes electrical power to be delivered to the fuel valve and ignition coil or starter. When the relay is de-actuated, the ignition coil is grounded, and the vehicle cannot be started with a jumper wire. A further switch is provided for disabling the relay.