Question about adding an ignition kill switch

dang

dang

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I plan on adding an ignition kill switch to several of my older vehicles but I'd like to do it similar to how a friend did his 2002 years ago. I can't contact him to ask so I thought I'd ask here. He used some kind of momentary push button switch that stayed connected when the power was on but disconnected when power is shut off. I think it's an NVR (No Voltage Release) switch but I'm having trouble finding it for 12v and the right application. It was a very small switch with a red button that was maybe 1/4" in diameter. He mounted it under the driver's seat, so you turned the ignition on, reached down and pressed the button, which felt magnetic, and then started the motor. As soon as you turned the ignition off the switch released and opened the circuit.

Anyone familiar with this type of switch?

Thanks,
Dan
 
Im not familar with what your talking about about my kill switchs kill the power from the battery , I use a large solenoid for battery cables and it is operated by a toggle switch , it requires a few other steps as well to stop back voltage from the Alt
 
bdigel said:
Im not familar with what your talking about about my kill switchs kill the power from the battery , I use a large solenoid for battery cables and it is operated by a toggle switch , it requires a few other steps as well to stop back voltage from the Alt
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Yeah, a battery cutoff is pretty common but you have to remember to turn it off (disconnect) each time. A momentary switch that stays on with power but off when the power is turned off is guaranteed to always work as an ignition cutoff.
 
A buddy of mine put in a RFID immobilizer after his Westphalia was stolen. He got it from an eBay vendor and has been happy with it. I'm not sure of all the details, but I expect it's method of not allowing the motor to run is similar to what Chris mentioned. I do know that if a thief was trying to steal it they would probably assume that it just wouldn't start as opposed to thinking that there was a kill switch somewhere that might get them to start tearing the dash apart looking for it.

I glanced at it on eBay and it looked like a pretty simple solution. I can ask him for details if anyone's interested.

Funny story about the stolen van - this guy is one of those people who sucks up all the luck in the room. He once had a Toyota van stolen and got it back with a like-new, very nice sleeping bag in it. The Westphalia was recovered the same day it was stolen. No real damage to it. The only thing missing was a few Mexican Cokes, a bottle of bourbon and a pair of cheap, backup binoculars. Oh yeah, and in their place was a Specialized Allez bicycle.

The cops told him: "We found your van. It looks like it's in pretty good shape. Your bicycle is still in it."
My buddy: "I don't have a bicycle."
Cops: "Well you do now."
 
I remember a little more about it now. He had a push button switch but it didn't have a spring on it. The button was loose, but it was mounted upside down under the seat and when the ignition was powered on you depressed the button and it stayed connected. It had a magnetic feel to it when it connected, which would make sense I guess. As soon as the ignition power was turned off by the key the button would fall down opening the circuit.
 
Ohmess said:
Looks like you could do this with a pair of relays and a momentary contact switch: https://www.the12volt.com/relays/starter-interrupt-diagrams.asp#psk
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I think my friend went the simple way and found a switch that worked like how I described above, but using one of those diagrams you posted might work good too. I'll have to spend some time understanding it. Thanks.

EDIT: I think this one will work.

This is a stand alone starter kill. It does not rely on an alarm or keyless entry for it to work, only a simple momentary contact switch (normally open) to deactivate it. Every time the ignition is turned off, continuity is broken on the starter feed wire. To disable (or start), turn ignition on, then press the hidden switch, then start as normal.
 

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Since I have my console apart to do some updating of wiring and adding gauges, I thought adding a kill switch might not be a bad idea. I know that often these are wired in to the ignition but it seems that wiring it into the fuel pump relay power might be a better idea. The engine cranks but won't start, which I suspect is a bit less obvious that there's a kill switch than a situation where it's clear that the battery isn't providing power. Regarding switch locations, clearly others have used the rear defroster, but I thought that this video showed a clever location. Granted, the video has been viewed 18M times so maybe it's not so clever a spot :)
The concept above of a relayed switch that automatically kicks disengages when the power has been cut off is also somewhat nice, since it means that you don't need to remember to activate the kill switch each time. Has anyone actually done the above wiring example? It would seem that instead of two 4-position relays you could just use a single 5-pole relay... @ScottAndrews you're the electrical guru...
 
e9Leveque said:
Since I have my console apart to do some updating of wiring and adding gauges, I thought adding a kill switch might not be a bad idea. I know that often these are wired in to the ignition but it seems that wiring it into the fuel pump relay power might be a better idea. The engine cranks but won't start, which I suspect is a bit less obvious that there's a kill switch than a situation where it's clear that the battery isn't providing power. Regarding switch locations, clearly others have used the rear defroster, but I thought that this video showed a clever location. Granted, the video has been viewed 18M times so maybe it's not so clever a spot :)
The concept above of a relayed switch that automatically kicks disengages when the power has been cut off is also somewhat nice, since it means that you don't need to remember to activate the kill switch each time. Has anyone actually done the above wiring example? It would seem that instead of two 4-position relays you could just use a single 5-pole relay... @ScottAndrews you're the electrical guru...
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I have a kill switch wired into my fuel pump relay. The disadvantage of this approach is that the car will still start if you have used it recently based on the fuel in the bowls. It won't go far, but it may not be where you parked it.

Were I to do it again, I would follow Chris' suggestion and interrupt the coil power. You have to remember to use this when you want it, but I would prefer this to something you need to shut off every time you go to start the car.
 
with megasquirt wiring to the in-tank fuel pump, it would be pretty easy to grab the power to the fuel pump as the 2 wires run from the computer, thru the interior to the gas tank. might have to look into this. i would want it fail-safed ON unless it is parked somewhere else, then maybe the switch would interrupt the power to the fuel pump. sound possible?
 
rsporsche said:
with megasquirt wiring to the in-tank fuel pump, it would be pretty easy to grab the power to the fuel pump as the 2 wires run from the computer, thru the interior to the gas tank. might have to look into this. i would want it fail-safed ON unless it is parked somewhere else, then maybe the switch would interrupt the power to the fuel pump. sound possible?
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I can help you wire something up
 
I realize I forgot to include the link to the video I mentioned above, it’s
He puts the switch underneath the leather of the shifter, which is somewhat clever since it’s not visible but easily switched. Regarding wiring, the question then becomes where to tap into whatever circuit you’re going to use. Fusebox area is easiest in terms of access but with the coil or fuel pump relay, where would people recommend the wiring go?
 
I have what Chris has: a fuel pump cutoff switch. Its a small button hidden within arms reach. As my car is injected. it will turn over when I twist the key but wont start unless I press the button and power up the fuel pump.
 
and is the point where you wired in the interrupt back at the fuel pump relay underneath the seat or did you do it up in the fusebox?
I know some people argue as well that a tap in the fusebox is somewhat obvious to the dedicated thief. At that point I figure someone is taking the car and there’s not much I can do to stop them. This is mainly just so that if I forget to lock the door and someone has a way to turn the ignition switch, they just can’t easily drive away
 
Ohmess said:
Looks like you could do this with a pair of relays and a momentary contact switch: https://www.the12volt.com/relays/starter-interrupt-diagrams.asp#psk
Click to expand...
Those schematics using two relays are to kill the starter - not the ignition (note that the thread is titled "Relay / Starter Interrupts").

To accomplish what dang had asked about would only require one, SPST relay (or a SPDT, or DPST, or whatever you have laying around). The schematic is dirt simple; I'll sketch it up if anyone would like.

​

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That was my thought as well, that one relay would work, although it would seem that it would work best in that case for the starter. At baseline switch is off, push switch to provide power through to starter and then can release the switch since power isn’t required to the starter anymore. For the fuel pump, one would want a situation where the lack of power running turns off the switch, then when you push the button you allow power to the fuel pump, but that then that button remains in the “on” position while the car is running and powered. Upon key and power disconnect the switch would open once again disengaging the pump. The description of a no-voltage switch would do it but I can’t find a 12v version of that. I’ll probably just go the conventional way and have a physical switch which I can turn on/off when I want to
 
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