Learn about one of the simplest means of protecting your car from theft, the starter interrupt. The types of interrupts are discussed, along with installation tips and instructions.
The starter interrupt (also called starter disable) is simply an interruption in the electrical current that flows to the car's starter when you turn the key. It ties in between the ignition switch and starter solenoid, and can take the form of either a simple switch or a relay (if part of a larger alarm system). Its purpose is simple: when activated, it keeps the car from starting.
Although bypassing a starter interrupt is fairly easy for an experienced thief, and it won't stop anyone from stealing your car stereo (it only prevents starting of the car), it will stop or slow down the casual thief.
If the starter interrupt is in the form of a simple switch, it is hidden in the car, usually in the passenger compartment under the dash. The driver simply flips the switch when leaving the car. A would-be thief would not be able to start the car without finding and toggling the switch. This means that they must locate it visually, or trace the wiring to find it. This delays the thief for precious seconds, hopefully causing them to give up and look for another car to steal.
If part of a more elaborate system, the starter interrupt is triggered when another sensor detects entry, disabling the starter before the thief starts trying to start the car.
Installation
You should follow the specific instructions that come with your unit, but we'll outline the process here. On some cars you can access and plug into wires in the central relay box, but on others you'll have to locate and splice into the correct starter wire. We'll assume that you're splicing into the starter wire. If you can find the manufacturer's list of wire colors for your model of car, (often supplied with your starter interrupt, or available on the Internet) the job of wire identification becomes much simpler.
To install, locate the starter wire - a good place is where it comes out of the steering column, a few inches under the ignition switch. It's best not to splice into the main starter solenoid power feed, since it draws a lot of current. You can identify this wire because it is fairly large, since it carries a lot of current. Instead, the wire to use is the small one going to the solenoid that energizes it when you turn the key to start the car. To find the correct wire and verify, using a voltmeter, turn the key to the ON position (don't start the car yet). Now, testing the wires one by one, find one with no voltage. Crank the car while watching the meter readout - if it shows 12 volts and drops off after the car starts, you have found the correct wire. The correct wire will show no voltage when the car is running.
