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Security System Questions
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=45&t=20758		 Page 1 of 1
Author:  Se7enLC [ Wed May 16, 2007 10:54 am ]
Post subject:  Security System Questions
So I just got an Interior Theft Sensor for my 2005. I haven't wired it in yet, but it seems simple enough.

It works by triggering a "rear gate open" when the ITS triggers. My question is how does this work? As far as I can tell, it does it by splicing a line onto the rear gate switch. The line is 12v when the gate is closed and 0v when it is open.

Is this a loop with a switch that is opened when the door opens? or is it an open collector that is grounded when the door opens? The only way I can see of attaching one wire to the sense line and change the voltage level is by shorting it to ground. Is that really what it does? I'll start pouring through the factory service manual, but I doubt it will tell me what is going on behind the scenes in those modules.

The reason I am interested is that I would like to add a hood switch and possibly a glove box switch to the alarm. I'm frankly very surprised that the hood switch isn't already in the system.
Author:  struggle07 [ Wed May 16, 2007 10:10 pm ]
Post subject: 
I think you are on the right track with the open collector thing. If I were doing it, I would take a piece of wire and momentarily tap the rear gate switch line to ground and see if that trips the alarm. Of course in doing that, you run the risk of damaging something if that is not the way the system is set up. But, I used to install professionally, and that seems to be how most systems (especially aftermarket) are set up--putting a ground signal on the wire to trigger the alarm.

If it is set up in this way, you should have no problem tapping the hood pin and/or glove box switch into the system.

Does this ITS sense motion or shock? Do you have a schematic for the ITS that you could scan and post?
Author:  Se7enLC [ Thu May 17, 2007 9:24 am ]
Post subject: 
struggle07 wrote:
I think you are on the right track with the open collector thing. If I were doing it, I would take a piece of wire and momentarily tap the rear gate switch line to ground and see if that trips the alarm. Of course in doing that, you run the risk of damaging something if that is not the way the system is set up. But, I used to install professionally, and that seems to be how most systems (especially aftermarket) are set up--putting a ground signal on the wire to trigger the alarm.


I found a relevant chapter in the factory service manual - about hood switches for the export models, and that sounds like how they do it (they mention pull-up resistor, which fits in with my theory)

Quote:
If it is set up in this way, you should have no problem tapping the hood pin and/or glove box switch into the system.


Here's hoping! I wish I could see the look on the next criminals face when they trigger the alarm when they don't expect to.

Quote:
Does this ITS sense motion or shock? Do you have a schematic for the ITS that you could scan and post?


The ITS senses shock, and it explicitly states that rocking the vehicle won't set it off. It suggests testing it with an open-palm hard but not-too-hard hit on the window glass. The unit is basically a box with a potentiometer adjust knob and 4 wires: 12V constant, 12V ignition, Ground, Trigger. There are a couple 1A fuses in line with the power wires.

I have no schematics for the box, but I do have the installation manual that came with it. It won't directly apply to the 05, but I think I will be able to modify the instructions to make them work. If that's the case, I believe that ANY chrysler ITs box will be able to be made to work on the liberty, any year, so long as it has a factory alarm.
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