Need help with kill switch with horn alert

I want to wire a kill switch that would cause an accessory horn or siren to go off if a would-be thief flips the switch. I have spent hours and hours reading and watching YouTube but I cannot find the specific instructions I need due to my more limited understanding of automotive circuits.

I have decided I do not want to wire a kill switch into the fuel pump line. Given the crap that is manufactured anymore, I don't want to risk a switch failure that would cause the truck to unexpectedly "run out of gas" while driving. We do a lot of driving in the mountains where shoulders are slim to none and guardrails aren't a given.

Instead, I intend to install two kill switches: one hidden switch on the clutch pedal switch circuit and another switch (plus horn alert) on the dash on the ignition circuit. I do understand thieves could still use a push start or tow or jump circuits elsewhere.

I did find a wiring schematic at https://www.the12volt.com/relays/starter-interrupt-diagrams.asp (bottom of page) for what I want but it involves four relays which creates a LOT of potential failure points. I'm hoping there's a simpler way to wire this up. One YouTuber suggested the use of a three-way switch but I didn't understand how I could close the circuit without the horn going off when I wanted to start the truck.

I have the following questions/needs:

1. A general wiring schematic or, better yet, a video tutorial, on how to do a kill switch+horn alert wire-up.

2. Some posts say to use a relay rather than a switch, but is that really necessary as long as the switch and wire are sized according to the load, especially since I'm not using the fuel pump circuit?

3. Can you direct me to a wiring diagram of the ignition circuit for a First Generation MT 4WD SR5 Xtra-cab with 5VZ-FE 3.4L engine? Or, better yet, provide me with specific instructions or photos on where on the wire to cut in a switch? (Perhaps there's another thread out there that I didn't come across?)

4. Magnetic reed switches would be easier to hide but I'm not finding a source for higher amperage switches (20 or 30A). Can you please link me to one? I'd put this on a hidden switch and locate the horn-alert switch in view on the dash.

Thanks a million, especially if you've had the patience to read this far. You all have been lifesavers for me when I've tackled other projects on my truck.

 

Things can change year to year best to have the correct schematics for your year vehicle

Why would any would be thief start flipping random switches ? Then you also need to figure out how to keep the Alarm being turned off by just flipping the switch back.

No plans to protect the cab so the window can be smashed the door opened cab stripped.

Why not just get a complete aftermarket alarm?

You want to disable the engine from starting !

You want to sound an alarm when the truck is what ? someone enters the vehicle ? ( not a factor) Attempts to crank the vehicle ? drags the vehicle on a Roll Back

How do you plan to arm and disarm the system?

There are so many different ways to go about doing this . We all have our own ideas

Why do write ups and post videos to educate would be thieves .

As far as the vehicle stopping on a one lane road Mechanical /Electrical devices can fail at anytime and any place.

Depending where you live people tend to ignore vehicle alarms because they are tripped all the time.

 

I am looking for a general wiring scheme for this setup that just shows how to wire a switch or relays to do what I want to do. It would be a perk to get specifics for my vehicle which is why I provided my vehicles specs.

Seems you've answered some of your own questions. As you noted, the public routinely ignores alarms so I'm not going to that expense but I'm a do-it-yourselfer so would like to do what I can on the cheap.

Kill switches have been around for many decades so I'm not asking for anything that isn't already known.

I have only a keyed lock so entry is relatively easy and I know of no way to protect from a thief breaking a window. I'm not too worried that a thief will be interested in stripping a 20-year old car with all-original equipment. And I already acknowledged in my original post that what I want to do won't guard against a tow.

But we're having a rash of car thefts of all types of vehicles. The cars are being driven away, not towed, often to just take them somewhere more convenient and more secretive to cut out the catalytic converter. So I'm hoping to guard against my vehicle being driven away.

Thanks for the opportunity to clarify. I WILL be preventing the car from starting via one or more kill switches that I will have to manually engage and disengage. I do understand (at a superficial level) the options e.g. adding a push, rocker, or magnetic switch or tying into an existing accessory that has to be engaged, perhaps only momentarily, to close the circuit (ignition or fuel pump or...) in order for the car to start or travel for only a short distance.

What I have read that can be done, and what I am hoping to get more details on, is to wire a kill switch so that if the thief does locate it and flip the switch, the horn or an accessory horn or alarm will go off so I can hear it in my house and know someone is trying to start the truck. But, yes, my question is exactly how can this be done so the thief (accidentally) turns on the horn but I don't. I can't imagine it so perhaps I've misunderstood the possibilities.

Fair point.

 

Buy quality components from a reputable distributor (not eBay or Amazon) and the least reliable part of it will be your own connections. Mouser or Digikey are my go to.


That said, I’d have to do a lot of digging to come up with something more helpful. Closest wiring diagram I have is for an 01.

 

Here's one that uses an SPDT but due to my ignorance, I don't understand how I can use this to turn on the truck without engaging the horn myself.

https://www.youtube.com/watch?v=ZYseqQSlPxQ

 

You have the drive by wire throttle body that would be so simple to disable.

Sadly I do not have the EWD for 2003 you can get all the data you need from All Data or Toyota`s TIS web site I have no idea if prices have increased last I used them was in 2017

You can easily install a switch in any of the systems grounds also attach a hidden pigtail to quickly by pass a failed switch . ECM ground on the left side of the Manifold . The ground for the circuit opening relay .

Just how would you like to have your audible alarm triggered? from the starter relay or from the starter solenoid ?

Another simple switch to arm and disarm .

Using relays would make this much easier.

I wish I had the schematics you need maybe someone will post what you need.

I wish I was close enough to help in person yes I guess I am paranoid as well.

 

Bivouac, thanks for your offer to help. I, too, wish you were closer.

I found an American-made Siemens prewired relay that does what I want to do which is to have the horn go off if someone tries to start the car without engaging a hidden switch. I'm happy to pay more than I would if I were to get the parts myself to make sure it's wired right.

https://www.americanautowire.com/sh...APhwtm3xutu-nfS-b8nbhHPvE2I0E178aApzdEALw_wcB

 

Looks like a standard aftermarket relay.

when the secret switch is one way, the relay directs current from the ignition switch to the horn.

with the switch flipped the other way, instead of the horn it runs the starter


Pretty simple, but trivial to override if the thief has time.

 

The sad part is at best it keeps the amateurs who get stupid from moving your truck.

There is no way I could build that for under $30 in just materials . Then I use top of the line parts.

If someone puts in a order for a truck that yours meets depending where you live it is as good as gone.

I would go with a better alarm then just a horn!!

If you can read schematics in a short time you can learn to figure out what ever you need.

Good luck