Originally Posted By: Neo Noodle

Originally Posted By: RyanA

Also, if you are hooking the relay as shown in that diagram to a true "armed output", you'll have a dead battery at the end of the weekend. Another easy way to make the circuit would be to put terminal 85 to the siren output if it's positive (most are), and 86 to the armed output. This way, voltage is only applied when the output is active and the siren is. Make sure you put the unlock wire from the alarm to the module side of the relay so it will still unlock the doors if you disarm the alarm.

Ryan

1 small computer relay will not kill your battery over a weekend.
The starter kill relay that ships with most all alarms uses more power and doesn't kill your battery.

Anyways hooking it up like that would be pointless.
The siren isn't active when they unlock your doors.
When they open the door that's when the alarm goes off & the siren becomes active.

Well, a starter kill relay does not energize until the key is turned. The power that runs the relay is the power from the switch that goes to the starter wire. When the alarm arms, the ground goes to one side of the relay coil. The other side goes to the switch side of the starter wire. That wire ONLY has power when you turn the key to the start position. That is why your battery does not go dead. And yes, a relay that is energized 24 hours a day from Friday to Monday morning will make your battery go dead.

How do I know this? I was a member of Code Alarm's R&D team in the early to mid 90's. I helped with design of some new circuitry in their alarms.

I guess the TRUE fail safe would be to put a switch that just interrupts your unlock part of the switch. Just use the alarm to do the unlock. Bottom line is this: If they want in the car, they'll get in there. A typical thief doesn't really care how they get in your car. Heck, why do you think the parking light output is fused now? On older alarms, you could simply break out a parking light, put a screwdriver in there to short it then set off the alarm. When the lights would go to flash, the main fuse would blow....

I guess one "failsafe" way would be to do it like this:

1. Buy a pulse timer and set it to 5 minutes or so. That way, you can operate the door unlock until about 5 minutes after you turn the car off. It shuts off after 5 minutes and there is no longer any current draw. The pulse timer would be set up to trigger when the key is turned off; that would keep the door unlock button working for that amount of time. On the internal relay, 87 would go to constant 12 volts, 30 would go to 85 on a relay. Also, 85 on the same relay would go to switched ignition. YOu would need to diode isolate these so the pulse timer would not backfeed the ignition source. 86 would go to ground on the external relay. 30 would go to switch side of unlock wire and 87 would go to the body harness side of the door unlock wire. Now, here's where you get to be a dick. Put 87a on the external relay to one of the grounding alarm trigger wires (hood switch, trunk switch, negative door trigger, etc). This way, when the little pricks try to unlock your doors, they are actually setting the alarm off. Nice and fun...