How to Install an Auto Battery Kill Switch

Written by g.k. bayne
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Installing a kill switch to disable all power to the starting motor can deter car theft. Modern vehicles still require power to be sent to other portions of the vehicle, such as for opening door locks and other on-board electrical systems. The option of connecting a kill switch into the starter motor circuit eliminates the ability of starting the car by any means. Of course, the switch is only as effective as to how well it is concealed. A basic manual switch can be installed almost anywhere inside the vehicle.

Skill level:

Things you need

  • ½-inch end wrench
  • 7/16-inch end wrench
  • Kill switch (rated for the battery)
  • Switch mounting hardware (supplied by switch manufacturer)
  • Battery cables (length is determined by position of switch)
  • Pocketknife
  • 4 cable end connectors
  • Crimping tool

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  1. 1

    Remove the positive (+) battery connector from the battery. Loosen the battery clamp's bolt with the ½-inch end wrench. Pull the connector from the battery.

  2. 2

    Use the 7/16-inch end wrench to loosen the cable clamps at the end of the connector. Pull the large battery cable from the connector. Trace the pathway of the large battery cable; it should be going to either the starter motor or the engine starter relay. Consult your particular vehicle's manual for the electrical circuit of the starter.

  3. 3

    Mount the new kill switch in a hidden location. There are many areas to securely mount the switch using the manufacturer's supplied hardware. Some kill switch kits come with a separate locked box that can be mounted inside the engine compartment. The box is typically black in colour and can only be accessed by a separate key. Other options include the hidden placement of the switch under the dash or the seat.

  4. 4

    Run two battery cables from the kill switch location. One cable will go to the battery's positive connection. The other cable will be attached directly to the starter motor or the starting relay. Consult the car manufacturer's specifications for the starting circuit's electrical layout.

  5. 5

    Use the pocketknife and remove approximately one inch of the outer insulation on the battery cables to reveal the bare copper strands of the cable's wire.

  6. 6

    Insert the bare copper ends into the cable end connectors. Use the crimping tool and secure the wire inside the crimp connector.

  7. 7

    Follow the kill switch instructions for the cable connections. Make all switch connections first. In general, the cable that leads to the battery connection will be attached to the terminal on the switch labelled as "battery." Connect the cable that is going to the starter to the switch terminal identified as "starter" or "starter relay."

  8. 8

    Connect the cable to the starter motor or starter relay. Follow the car manufacturer's installation instructions for your particular vehicle. Attach the cable to the positive terminal on the battery.

Tips and warnings

  • Do not allow the positive battery wire, when connected to the battery, to come into contact with the car's metal frame. A direct short circuit can occur, causing damage to the battery or other electronic equipment.

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