old school hi/low beam switch

I once saw a 555 timer circuit that killed the ignition after a delay and it would repeat that cycle until disabled.
The advantage being "nah - it's not a kill switch, it's a fauly car - let's leave it".

The disadvantage being being that it's gotten to the freeway or railway crossing when the above decision is made.


As with any kill device, what is the risk if it fails?

Many oldskool ignition-kills simply shorted the coil- to ground (chassis) hence killing the spark. But this could be easily defeated by cutting non-standard wiring.

Others work by having to energise a relay to supply power to he ignition or coil. But if that relay failed, the engine would never start.
But if it was an SPDT/changeover relay that disconnected power when energised - and it was energised if ignition was on unless somehow disabled, it was more "failsafe". (IE - relay off meant ignition as normal.)

What's best? You decide....

Then there is activation.
A hidden switch? But what if they find it?
What about a few switches - hit the wrong one and it closes a relay that shorts the +12V ignition supply to chassis thereby blowing a fuse. No problem for you because you know where you hid the spare fuses, but will "they" bother?

I liked combination switches. A keypad would deter most wannabe thieves. And since they usually controlled a relay somewhere, you could have a mechanism to bypass etc.

So many ways.....

My car is so rare I just take its distributor rotor (yes - it's old!) - they may be smart enough to diagnose the problem, but few would know what rotor to fit (especially since my dizzy isn't from that model anyhow!).

Otherwise for modern vehicles - from a reliability & safety POV - I'd probably want something that disables the ignition - ie, prevented the ECU main rely from energising until the hold-off (disabling) relay was deactivated.

But I also have a paging alarm which I intend to set to an auto-destruct sequence unless disabled (as all good intergalactic starships, oil-tankers, trains, semi-trailers and trucks have in case they ever run out of control or have undesirable aliens on board).

the best kill switch by far is called a key

7rrivera7 wrote:

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I know some fabrication is in order but I want to get some feedback and maybe a source for this type of switch from people who have done it. Thanks!

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  no fabricaton needed, it just mounts down. as for a source, any auto parts store has them. $12 or so last time i bought one.

ckeeler wrote:

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7rrivera7 wrote:

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I know some fabrication is in order but I want to get some feedback and maybe a source for this type of switch from people who have done it. Thanks!

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  no fabricaton needed, it just mounts down. as for a source, any auto parts store has them. $12 or so last time i bought one.

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I'm pretty sure I'll have to fab up the swich mount as the original switches went right into the car's floor pan. I want the switch to be hidden under the carpet and flush against it otherwise a thief might notice it protuding.

Simpler a(nother?) fog light switch carrying the starter circuit? You will need a switch with a 10amp plus rating or add a relay, ignition controlled such that the starter wouldn't operate without the switch being thrown. to match your existing switches. Actually I'm with KP on this; an ignition key.