On Mon, 22 Oct 2001, Lawrence Lile wrote:

> I'd like to re-open the topic of practical car theft prevention schemes.
> This is a hot topic for me, as I had a nice, fancy, almost new and one month
> old car stolen right out of my driveway this weekend.  Burns me up.

I feel your pain.  Sucks when you forget to lock it -- I assume you did
just forget, right?

> 1. Interrupt the line to the starter solenoid with a switch or relay.
> Either hide the switch in a wierd spot accessible to the driver, or connect
> it to a coded keypad.

Lotsa commercial systems do this...

> 2.  Is there an electronic way to disable an automatic transmission?  Some
> solenoid that engages something that could be disabled?

Depends on the car, I would imagine.  I know mine all have mechanical
links from shifter to transmission...  it would be easier to prevent the
engine from starting, I would think.  There are lots ofways to do that.

> 4.  Disable power to the distributor with a special switch.

Haven't seen a new car with a distributor in quite a while.  Most do have
a coil pack you could disable, but a lot now have individual coils for
each cylinder, fired by the engine computer.

> 5. Disable power to the electric fuel pump.

Very easy.

> 6. Affix a 555 driven transistor to the horn and stereo and activate it if
> the driver doesn't enter the secret code within xxx seconds of starting the
> car.

Plenty of commercial systems do that too, along with most of the above
items.  Of course none of that will stop a tow truck or flatbed if they
really want it.

> Now obviously, a real pro could defeat this stuff, but we're probably not
> going to stop a pro anyway.   My car was not locked, and some kid probably
> tried a few car doors, found one open,  jumped in, drove it down and pushed
> it into the river, or sold it to a chop shop.

If I were worried about my car, I'd start with the door locks...  then add
a dummy flashing red LED or two, code pad that disables fuel pump power
and coil pack power, plus maybe one or two other critical sensors like the
crankshaft position sensor.  My fuel injectors fire individually, so
disabling them would be a pain in the butt.  Last I'd add a LOUD horn
activated if the person opening the door doesn't enter the correct code in
some reasonable period of time.

Personally, I'd mount the code pad in a visible or at least easily
accesible spot, then bury the guts somewhere difficult to get to, with the
relays or whatever remotely monted.  Make it so that ripping out one part
doesn't defeat the system.  I have looked at some commercial systems, and
have not thought they were really worth the money.

Dale

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