passive starter kill with a switch

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i was looking at this relay wiring diagram and i was wondering why must you use two relays...wouldnt i be able to just use one relay and do the same thing? Can i just trigger a single relay and have that same relay connect the two ends of my starter wire?

thanks,

Jerry

No because that turns it into a push-button start!
In practice it's pretty useless, I can disable any aftermarket immobiliser in about 15 minutes, no point without an alarm to alert the vehicle owner.
This is using a single relay:-A5F_untitled.bmp

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

The diagrams are identical, I took the NEG side of the coil and switched it, you took the POS side and switched it!
Both are effectively push starters.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

aaahh i see now where i was reading wrong. i got confused when i seen ignition switch on 87.  makes sense now. Now if i wanted to start the vehicle by pressing this button rather then cranking my key can i just add a 12volt supply to contact 30 and tap in to my vehicles starter wire with contact 87? it makes sense to me that it would work but not sure if its safe with out burning anything. reason why i ask is because my vehicles key cylinder or key tumbler what ever its called, doesnt always work. so i would like to just have a button to crank it for me.

Your source at 87 should be a constant, fused @ 20 amps. 30 goes to the starter motor though in this instance it doesn't matter which is which.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

great thanks. But what is the reason for having two relays in the first diagram. it almost seems to me like the second relay (the one with the bush button) is useless.

All I can think is a latching effect, where once ignition is removed from the right hand relay you're automatically immobilised but there our arrangement achieves that anyway.
So like you I don't understand it but unlike you I don't care!
P.S. I used to have a Mercedes CE Coupe and the starter part of the ignition switch failed. I simply used one of the two circuits we came up with, it honestly doesn't matter which and had the car another two years.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

howie ll wrote:

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In practice it's pretty useless, I can disable any aftermarket immobiliser in about 15 minutes, no point without an alarm to alert the vehicle owner.

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Howie, the above comment caught my eye. What if the kill switch does something more elaborate than interrupt the starter wire?

For example, it's common for vehicles to not start unless the shift lever is in "Park" (or the clutch is depressed). What if a kill switch modified those circuits, causing the vehicle to believe the pre-start condition wasn't satisfied? Would that be harder for a thief to figure out?

What if a kill switch did that *and* interrupted the fuel pump? And, the kill switched was a reed switch hidden behind the door panel (using a magnet to activate), and therefore not detectable?

Or, what if there were two kill switches? An obvious one for the thief to waste his time on, and a more obfuscated one like mentioned above?

Is there an ideal DYI kill switch from your perspective?

Regarding your comment about alarms. I've read they're easily disabled (ripped out) by thieves in 1-2 minutes. Do you believe a one-way alarm is a waste of time? Are there downsides to two ways, such as more drain on the car's battery as it communicates with the remote?

Thanks for your time. If this post is better suited to a different area, please move it. (I tried to post to "security and convenience." I don't have the privilege yet to start new topics.).

First that applies to to manual transmissions only and not all of them. there's a neutral position sensor on the gear box, the engine management has to see a ground when the lever is at neutral, cut that and it shouldn't start, the clutch switch is a better bet though.
You don't want to cut anything that affects a vehicle in motion such as fuel pump, ignition, engine management, too dangerous, a faulty joint go go open circuit and suddenly no engine at speed.
The problem with all these switches is the hassle just isn't worth it, also don't forget most modern cars have a factory immobiliser, will only start with the right chipped key.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thanks Howie. I hadn't thought about ignition or fuel interrupts having unintended consequences at speed.

BTW: Regarding the transmission/start interrupt, automatic transmissions (at least in the US) have a park/neutral switch which prevent interrupt the starter circuit. I was thinking of doing something with that switch, making it look like it's not in park/neutral unless the kill switch has been pressed.

I'm also thinking about a traditional kill switch (interrupting the starter from the ignition switch) just as a "honey pot." Something for the thief to say "ah, there it is. I'm so smart. This owner's such a dope." And then (hopefully) get even more rattled when bypassing the obvious doesn't work. I.e., maybe he'll spend more time fiddling with that. Or, if he commences looking elsewhere he'll have a doubt whether he should have spent more time on the obvious kill switch.

You mentioned factory immobilizers. The 2012-13 Hyundai Accent doesn't seem to come with this in the US. I'm trying to track down whether it comes with the connections/components so that it could be enabled. For example, there's supposed to be a connector in the steering column for the transponder/key antenna. And, a connector up high in the dash for the immobilizer module. I'm trying to find out if those connectors are present (and, even better, have the bits plugged in).

I'm wondering if it's as simple as simply buying a chipped key and taking it to the dealer to have them use their computer interface to "learn" the key.

(Or, perhaps, buy the bits to plug into those two connectors. Then buy the key. That would be a risky proposition because there's more to it. The PCM and ECM modules have some immobilizer stuff built in. There would be a risk those are neutered in some way. And then it requires a cooperative dealer doing something outside their normal procedure for the car. I'm not too hopeful this will pan out.).

Again, if this topic is better suited for a different area, please move it. (I couldn't start a new topic as a new user.).

I'm well aware of Park/Neutral inhibitor switches on auto boxes but again is it on the gearbox or gearshift? Is it all worth while especially when your vehicle does have a transponder immobiliser.
You are actually worried about the one crooked locksmith in a thousand who has the extremely expensive software which enables him to turn off the immobiliser (and I'm not even allowed to tell you how), that's after he's broken into your car and the preferably aftermarket alarm system hasn't frightened him away?
Seek treatment for your paranoia, this whole thread is moot with reference to your vehicle, totally unnecessary.
Just get a decent alarm and use it!
The point is apart from the factory alarm, nothing you've suggested will stop someone like myself who makes a partial living from rescuing broken down vehicles.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

howie ll wrote:

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Is it all worth while especially when your vehicle does have a transponder immobiliser.

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Howie, thank you very much for your time. Your answer makes absolute sense for a car with a factory immobilizer (chipped key). Unfortunately for me, 2012-13 Hyundai Accents don't seem to have this in the US. In other countries they do. (On another forum for this vehicle, that's the unanimous consensus.).

That's why I'm considering how to do a kill switch, and particularly an obfuscated one. (I'm going to do an alarm too.).

Well they are probably wrong because both DEI and Audiovox/Code/Prestige list this vehicle as having one.
Two ways to find out.
Do you have a security light on or around the instrument panel?
Remove the steering column cowling and see if there's plastic around the ignition switch with two or more wires exiting it.
If yes to either you have one.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

howie ll wrote:

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Well they are probably wrong because both DEI and Audiovox/Code/Prestige list this vehicle as having one.

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I've confronted this topic a few times. It's definitely perplexing. Enough that I still had lingering doubts when I replied to you. But, I just pulled the cover and the wires are not present from the ignition to the connector. (I'm looking at the Hyunda1 Accent wiring diagram which shows 4 wires. Two for the antenna, ground, and 1 for the "key in switch" signal to the BCM. All it has is the ground and BCM wire. The antenna wires are definitely not present.).

It's confusing because other countries have it. Canada, Australia, et. al. The manual describes it. But, the wires are not even in the loom, and the SMARTRA unit is not present under the dash.

So, I'm probably going to have some questions about kill switches. Be gentle with me. It's not my fault I live in the wrong country. :)

I'm definitely going to do an alarm. I've had my dash panels removed, exploring wires, making sure I completely understand what I'm going to do, measuring voltage and state changes, etc.

I probably won't put much stock in its built-in kill switch. I'm going to want to do my own obfuscated switch. Maybe a toggle switch under the hood to kill the fuel pump when I'm away from the car for more than a short time (or, the area gives me the heebie jeebies.). I take to heart what you said about interfering with components which could cut the engine at speed. That's why I'm thinking of a very solid on/off toggle hidden somewhere as an added layer of security (but requiring more effort in return for greater reliability at speed).

I'm just toying with ideas.

I really appreciate the time you give to my questions! I'd like to buy you a pint or two.

Oh for all we curse it, at least the EU (overpaid clutch of Civil Servants in Brussels) at least they standardised the damn things on ALL vehicles on sale (not just manufactured) in Europe from 1/1/97.
Of course the last test is a hot wire!
Constant to ignition 1, then flash the starter, try this with the ignition key well away from the vehicle.
There are lots of clever places to interrupt, fuel lines, engine management, clutch, starter, the last two being the only 2 I would recommend.
The problem being with all the best will in the world soldered joints do give way, OK yes it happened to me in 1985, luckily I learned.
Thus an interrupt to affect engine run rather than start isn't safe, do-able but not safe.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.