I'm having a bit of a problem with my DEI 520t battery backup. I'm hoping someone that knows more about how it works can point me in the right direction. I have it hooked up a little bit funny, and I'm not quite sure what I need to do to make it work correctly.
First off, vehicle is a 2006 Ford Mustang GT, alarm is a Python 991. Problem is this: when the car remote starts, the 520t triggers the alarm the second the starter engages. (Voltage is showing around 10v at this point.) Vehicle battery is charged, backup battery is showing 12.3v. If I disconnect the backup battery (not the module, just the battery) the car will start. Blue wire is "triggering" even when the alarm is off and I start with the key, so I don't believe it to be an issue with the remote start of the equation.
The hookup is similar to the second post of
this thread. I'm powering a Bosch style relay when the 520t triggers, using a TIP42G transistor. Connections are as follows:
520T:
Red: +12v constant
Gray: Alarm brain +12v constant connection
Blue: Base pin of transistor
Black: ground
TIP42G:
Base: blue (-) trigger from 520t
Collector: ground
Emitter: pin 85 of relay.
Relay:
30: trunk pin (-)
87a: alarm instant trigger (-)
87: N/C
86: +12v constant
85: Emitter pin of transistor
The idea is that my trunk pin is normally closed, so it passes through the relay unless the 520t triggers and pulls the relay on, which breaks the ground on the (-) instant trigger wire. This part works, the problem is that the 520t is energizing the relay while the car is cranking.
Any ideas on how I can fix this? (Preferably without running a new trunk pin!) I'm thinking either my 520t module is defective, or the transistor is amplifying the trigger and making it fire off the alarm at a much higher battery voltage than normal.
Okay, I figured it out. I wanted to post the solution back here in case anyone else ran into this.
I just added a ~10k resistor between the transistor and the 520t. That seemed to fix it right up. I was even able to add my tilt sensor onto the same line (diode isolated of course) and it works fine as well.