Ignition Switch

[rj_darlow]

G'day,
I've been wondering about putting a "starter" button in my car. It's for security, not for trendiness (the car is an AE82 Corolla). I was thinking about taking the 'start' wire out of the ignition barrel and running it through a relay with the coil on the relay being switched by some form of switch on the dash. Not exactly stealthy, but if it looks like a switch for lights then people won't suspect it... Kinda like a kill switch. If that doesn't make sense I could draw a diagram.

Anyway, what I was wondering is this: Is this the right basic design? If so, what current ratings would I need on the relay? The wires into the ignition barrel aren't massively thick, so if the current that runs through them isn't above 20 or 30 amps then there may not even be a need for the relay, as I assume there is another (much bigger) relay somewhere between the ignition barrel and the starter.

Thanks in advance for any advice or replies.

Cheers,
Richard.

[Dale]

The wire running from the ignition barrel to the start is only a trigger wire, the starter draws it's real current directly from the battery, therefore it doesn't need to conduct a huge load of current through the wire that runs from the ig barrel

Do you want it to be a kill switch, or like a push button starter? Ie. will you still turn the key to start the car or will you push the button?

Either way you shouldn't need to use a relay for it.

[rj_darlow]

G'day,
Thanks for the quick reply. Not too sure if it will be kill switch or starter... Depends on the switch I choose from Jaycar. Probably a momentary toggle switch, so I guess that makes it a starter. Key will be turned to ON and then button used to start.

[Dale]

Yeah I've put them in cars before, just have to cut the wire going to the starter at the ig barrel, get a +12v that doesn't drop when the motor is cranked over (at the ig barrel), run that through the switch and back to the now cut starter wire running to the engine bay.. when you push the button the starter gets +12v and kicks over.. and only works when the key is in the on position
Wire rated at 30amps would be plenty good enough for the task.

edit: the +12v you get shouldn't be a constant +12v, it should be an ignition +12v that doesn't drop below 12v when the motor is cranked.. was a bit vague with that

[mrshin]

If in doubt, much better to also fit a starter relay

[Sigmeister]

If you are doing it for security reasons, a better option may be to make one of your momentary action switches in the car your starter.
So you put the key in, turn it to on, then push something to start the car.

Some ideas would be, windscreen washers, horn, high beams, heater.

So you add a swith and a relay so that you can flick the switch to use the button to start the car, then flick it back so the button returns to normal use.

[PlacentaJuan]

a guy on the cressida forums did one of these, im pretty sure most ignition barrels are the same so it should work on your car.

instead of a switch you could be really high-tech and use a fingerprint scanner, they are pretty small and cheap now - BIOMETRICAL SECURTIY OMG !!!!

http://thermactor.com/forum/viewtopic.php?t=9932

[BeRad]

nothing a wack from a shifter from the 12v battery wire on the starter to the trigger wire on the starter wont solve ......

i think youd be better off with an immobiliser, if they want the car the above statement will get them the car.

[JetspeedCamry]

Was just wondering, even with this extra switch, would someone still be able to hotwire the car? The wiring would all still be there for them to apply 12v to? Would cutting the ig. switch wire also lockout the use of the key starting it?

This is the same setup they run on the Nissan 350Z...key to ON, wait for confirmation beep and then press "START".

[BeRad]

as i said pop the bonnet and short the trigger wire to the constant supply to the starter, providing the ignition barrell is wired to on, your off and away.

[WDE_BDY]

Yep, 12V to three sources will get most cars started, starter, ecu and fuel pump. You need more lateral thinking with security these days, cut circuits that 12V won't bypass like important sensor wires for the ECU etc.

Callum

[rj_darlow]

G'day,
Thanks for the replies.

nothing a wack from a shifter from the 12v battery wire on the starter to the trigger wire on the starter wont solve ......

i think youd be better off with an immobiliser, if they want the car the above statement will get them the car.

Yeah it's a good point. It's not really so much to make the car unstealable, just a bit of a deterrent. I know if someone really wants to steal a car then they will. Immobiliser is a possibility, it's just the car doesn't really warrant a fantastic alarm system and as I don't have comprehensive insurance then there won't be a reduced premium.

If you are doing it for security reasons, a better option may be to make one of your momentary action switches in the car your starter.
So you put the key in, turn it to on, then push something to start the car.

Some ideas would be, windscreen washers, horn, high beams, heater.

So you add a swith and a relay so that you can flick the switch to use the button to start the car, then flick it back so the button returns to normal use.

Thanks, that's a good idea. The original intention was to just disguise the switch as something like driving lights, but that's going one step better.

Thanks again, now I know that it should work with relative ease.

Cheers,
Richard.