dei 520t battery backup, viper 5900

I recently decided to add the DEI 520T battery backup to my VIPER 5900 SST alarm. I connected it as follows: RED: to the ignition harness constant 12V wire BLACK: to a ground BLUE: to the Primary harness blue wire. I am using the blue wire for the trunk trigger, so I spliced into it. So again there are now two negative triggers (trunk and battery) on this wire. GREY: To alarm module 12V input. So the battery backup works. If i trigger the alarm then disconnect the battery, the siren still sounds. HOWEVER, if I disconnect the battery with the system armed, it does NOT trigger the alarm. The blue wire is functional as If i manually ground it, the alarm is triggered. Another question... it says not to use this battery power high current things like lights, etc. However, since the battery output is tied into the alarm input, and the alarm input is wired into the ign harness power wire... the battery provides power to the harness. So if the main battery is disconnected and the alarm sounds, wouldn't the backup battery also be powering the lights? (since the parking lights flash with the alarm trigger)

Well I did some additional testing. When I use a multimeter and measure the current on a regular output (negative) trigger wire, it measures current when the output is triggered. However, if i measure the blue wire directly off of the 520T module, NO current is measured when the system is armed and battery disconnected. I presume the backup battery module measures a voltage drop across the constant 12V wire and that triggers it? But now that I think about it, since the backup battery wire is constantly providing power to the constant 12V wire thru the alarm input wire, there will never be a voltage drop across the ignition harness constant 12V wire.

Is the power wire of the 5900 that you connected to the grey wire of the 520t also connected to the constant wire in the ignition harness? Is is not supposed to be.

JWorm wrote: Is the power wire of the 5900 that you connected to the grey wire of the 520t also connected to the constant wire in the ignition harness? Is is not supposed to be.

Yes. The 12V input to the 5900 module is connected to the red ignition harness constant 12V wire. The grey wire from the 520T is connected to the 12V input wire, hence indirectly connected to the ignition harness wire. I don't see how you would not connect it to it?.. unless I find a different source for the alarm 12V input.

The 12v input of the 5900 goes to the grey of the 520t. That's it. The rest of your connections are fine.

JWorm wrote: The 12v input of the 5900 goes to the grey of the 520t. That's it. The rest of your connections are fine.

oh LOL. I see now. I need to disconnect the 5900 power feed from the harness and have it solely connected to the grey wire. Gothca.. THANKS!

ralliart16 wrote: JWorm wrote: The 12v input of the 5900 goes to the grey of the 520t. That's it. The rest of your connections are fine. oh LOL. I see now. I need to disconnect the 5900 power feed from the harness and have it solely connected to the grey wire. Gothca.. THANKS!

I'm a little confused. So the alarm is not connected to a 12V constant power source? The alarms 12v red wire only goes to the 520T gray wire?

Yes that is correct Mechanix.The 520 works like this.If it loses constant 12v feed from vehicle(red wire),it instantly switches to the battery for power(gray wire) to power alarm module."ole blake"

I'm about to install my 520T in my car, since my neighbors civic just got his rims jacked. They pulled out his window and opened the door, popped the hood, and just disconnected the battery..and no more siren. No one even heard it, so it must of been fast. So with my constant 12v red wire from my alarm. I cut it. Run the alarm side to the gray wire, and the other 12v end that I just cut to the red 12v 520t wire. Then the blue wire to my -blue trunk trigger wire. My alarm is a python 990 if any one was wondering. Also I want to add another shock sensor. Can I just splice one into all the same 4 wires from my other shock sensor..or do I just connect it to the green wire?

Resurrecting this thread with a question. I have the multiplexed blue wire of the 564T connected to a dual zone radar sensor. If I want to add the 520T Blue wire to that trigger input, do I need diodes on both the radar sensor & the battery backup outputs? If so, do the diode's stripes face the security system module or reverse?