I'm working on a home brew alarm system for a 1990 350 Ram van. I'm looking for a good way to disable the vehicle entirely in case a thief gets in past the alarm and tries to hotwire and drive off with the van.

Ideally, I would like to install a switch or relay in one of the wires under the dash that would prevent the engine from running. The dash wiring is preferrable to in the engine compartment or under the hood because I don't have a convenient way of making a reliable and tidy connection through the firewall.

Unfortunately I don't have the Haynes or Chilton manuals for the vehicle.

Any suggestions or general notes about how to approach this would be appreciated.

Thanks,
Adam

 

Interrupt the wire coming off the distributor.

 

Second that

 

Thanks for your replies. The distributor pickup/hall effect sensor wire was my first choice, but I didn't want to run a wire around the top of the engine, and (lacking a shop manual) wasn't sure where to access the wire on its way to the computer.

What I've done instead is to interrupt the wire to the ASD/fuel pump relay. I've run the wires from this in through a hole in a sort of rubber plug in the firewall to the right of the steering column, and then to a switch hidden under the dash. It seems to work as desired.

Thanks,
Adam

 

A good auto thief can find any thing you add to the vehicle.
What you really need is to put the disabling device on a time delay.
The thief hits the street with the vehicle and a minute later the thing stalls in the middle of the street. No thief wants to be in the middle of the street with a freshly stolen vehicle.
I vote for a fuel pump disabler, simple and easily accomplished.
My neighbor, that I didn't know at the time, had a new Tahoe stolen from his driveway. I watched it happen I thought it was being repossessed, broad daylight on a Saturday morning. Profession looking slant deck wrecker shows up, uses a set of master keys to open door, drags it on the bed with the alarm sounding and drives away.
A year later I discovered they actually stole his vehicle, I never told him I watched it happen.
There in no way to prevent this type of theft without a 24 hr guard.

 

If you believe a "good thief" can find anything you add to the vehicle then I'm not too sure I understand your recommendation to install a fuel pump disabler. Simple and easily accomplished also means simple and easily circumvented.

Actually, I don't even understand the original motivation of trying to disable a 23 year old Dodge van in the first place. Unless it is pimped out to the level of multiple thousand$ who the hell would want to steal it?

 

......

 

I don't know of too many thieves that will take the time to remove the doghouse to look for a break in the distributor wire.

 

Good point I'm part of a music group, and we usually have to unload an entire van worth of instruments and sound gear into a hotel room every night and then load it out again the next day to do a show. Gets old really fast.

The immobilization is only one part of the system. The rest of it uses a microcontroller wired to the door switches and an accellerometer to detect intrusion or vehicle motion. (We've also got a laser that will be reflected around the perimeter inside the windows, but that's for version 2).

When the controller gets triggered, it will start honking the horn and send alert tone over a GMRS radio, which should be able to reach us anywhere within about a 500 meter radius. (Once we get the right antenna, we'll also get a text message through a GPRS modem when there's an alert.)

The plan is to only use this system when we are nearby enough to 1) get the alert, either by hearing the horn or through text message or GMRS radio; and 2) get to the vehicle fast enough to shoo the thief away before they drive off with our gear.

As long as it takes a few minutes for them to figure out the immobilizer and get it working, we should be okay.

This sort of operation is our greatest concern, really. How long did it take them to make off with the car? And what did they do once they got inside it? Undo the parking break?

We will probably remove the door lock pull to help prevent the screwdriver and coathanger sort of forced entry, but that won't help against a master key.

Even with the gear inside, the total value of the van will still be way below the value of a cheap new car, and hopefully a thief would realize this. But, can a car thief be trusted to make reasonable choices? I'm not sure

I don't know much about car thieves and alarms, so if anyone has suggestions about how to make this as thief and fool-proof as possible, let me know.

Cheers,
Adam

 

I was commenting on the original post about preventing the van from being stolen. Now, with more info from AFM we certainly know why he wants to protect it.