Since 1-1-2019, ARA requires a Master Electrical Disconnect Switch (or kill switch). Here are what the current rules (2021) say:
Which kill switch to choose?
You need at least a 4-pole switch (2 poles for the battery, 2 poles to kill the engine) but can also run 6 poles (2 extra poles to drain power from alternator to prevent power spike). A good 4 pole kill switch will cost around $40: (http://www.amazon.com/gp/product/B012UW1GAI)
A better but more expensive option (~$300) is to use a Cartek GT solid state kill switch (https://rally.build/collections/rally-build-fabricated-rally-parts/products/cartek-gt-solid-state-battery-isolator-kit), much safer as you don't have to run high gauge wires through the car (see video below for the comparison), it is also a much lighter option and makes it easy to install an external kill button:
4 pole kill switch install
Using a 4 pole kill switch like this one (http://www.amazon.com/gp/product/B012UW1GAI) 2 poles are used to disconnect the battery and the 2 other poles are used to kill the engine while running from the alternator. Make sure you use the appropriate wire gauge (4 gauge min to battery (http://www.amazon.com/feet-gauge-red-battery-cable/dp/B002DZF1MW), 10 gauge to ignition). The installation steps are as follows:
1. Disconnect both negative and positive battery terminals
2. Remove nut to disconnect starter and fuse box cables from positive terminal
3. Connect the kill switch in series by running 2 wires, one to the positive terminal and the other one to the starter/fuse box wires. Make sure to use firewall pass through connectors (https://www.amazon.com/Fastronix-Premium-Current-Terminal-Connectors/dp/B079K5HB79) if you need to go through the firewall as regular grommets might fail with vibrations. See picture below:
4. For the 2 remaining poles, the easiest solution is to directly kill the ignition by wiring them in series with the ignition fuse or the ignition wire going to the key (the remaining active components of the system like the fuel pump will drain the power from the alternator).
If you choose the ignition fuse route, here is an example on a 2004 Subaru STi. The ignition fuse is located in the fuse box on the driver side below the steering wheel. You will need an inline fuse holder to keep the ignition fuse, make sure you use the same 15A fuse in the fuse holder.
Several techniques to attach the wires to the fuse box:
- Use an available fuse tap kit (e.g. http://www.quadratec.com/products/13029_200.htm)
- Cut the fuse in half, remove the top plastic to expose the connector and weld a wire to it
- Cut a wire connector in half and it will perfectly fit in the fuse box plug (technique used on the install below).
If you are tapping the ignition wire that goes to the key, you can look at the video below (that also relocates the wiring to the key). This is a much cleaner solution if you have a car that does not have an immobilizer that requires a signal from the key.
5. Cover all the connectors with rubber boots and heat shrink wrap
a. Car off, switch off: turn the ignition key, nothing should happen, starter should not crank
b. Car off, switch on: turn the ignition key and start the car
c. Rev the car up to 2500rpms and turn the switch to the off position: engine should stop.