I install car alarms for a living and have seen hundreds of theft recovery. And many of them had an alarm but were easily defeated by unplugging the brain. The reason for this is because the alarm sends a ground signal to the starter kill relay when armed. But if you unplug the brain, the signal is lost and the relay keeps the ignition side and starter side connected in their Normally Closed position. DEI calls this a Fail Safe starter kill because if the alarm were to malfunction, the starter will still work. Usually a remote start alarm will already function like this upgrade because the starter wires loop into the brain without a relay and won’t connect if the harness is disconnected.

An easy way to upgrade your starter kill is as follows.

You need an extra SPDT automotive relay and a soldering iron.

There will usually be a few wires off the alarm that are not used. Usually auxiliary output wires. We are going to use two of these wires if available but one is fine too.

Open up the brain and cut the pins so that they are no longer connected to the circuit board. And solder the connector sides together so that the two wires make a loop inside the brain.

One of those wires will go to ground. And the other will go to the 2nd relay. If you only had 1 wire available, after cutting the circuit board side, solder it to the ground pin but don’t cut the ground circuit.

This is so that if the brain gets unplugged, the 2nd relay will lose its ground wire and the starter will not work.





It goes without saying that hiding the relays is an integral part of the installation. And the point at which the starter wires are connected to the vehicle, should be as hard to see and reach as possible because a determined thief will just reconnect the factory starter wires together.

That’s it. Should only take 10 or 15 minutes longer than usual but gives you an added layer of security without the hassle of a hidden toggle switch.




I don’t frequent this area of HT so PM me any questions that you may have.

I know disconnected is spelled wrong. I must have dyslexia.