Need help building relay.

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=27457
Printed Date: July 19, 2025 at 6:10 AM

Topic: Need help building relay.

Posted By: yeager
Subject: Need help building relay.
Date Posted: February 29, 2004 at 3:02 PM

Need help configuring a relay/latchting switch.

2003 gm avalanche, link to wiring diagram of this vehicle https://www.chevyavalanchefanclub.com/attachments/2003_alarm_wiring.zip

Attempting to control a negative/neutral line attached to added pinswiches on tailgate and saddle bags which turn on cargo area lights and also sets off factory alarm. The ground line on the pin switches is tied into the right rear door trigger at the bcm, which sets off the facory alarm if they are opened. Diode on line stops cargo lights from coming on when a car door is opened. Problem is that interior cabin lights come on with cargo area lights when the tailgate is open since computer(bcm) thinks a car door is open. The ground/neutral line to the bcm(door trigger) needs to be controlled. Ideally it only needs to have continuity when the alarm is set to arm. Can come close to this if it can be controlled under the following conditions:

The ground/neutral wire(attached to tailgate pin switcn) needs to have continuity to door trigger when the doors are locked(neg. signal from gray wire at lock/window module) and only if car is NOT running.(+12v run wire).

The ground/neutral wire needs to Not have continuity when car is unlocked(neg. signal from tan wire at lock/window module).

Continuity changes need to remain constant until changed by unlock, lock, 12v run, etc signals.

Please help.

Replies:

Posted By: Toru
Date Posted: March 01, 2004 at 5:30 PM

"Ideally it only needs to have continuity when the alarm is set to arm."

The killer question is: Does the factory alarm have an "active when armed" output? This may not be dedicated - you might be able to tap some other output that happens to be active when armed.

I can't make heads or tails of the diagrams, since the larger versions of the schematics were not included in the zip...

Posted By: yeager
Date Posted: March 01, 2004 at 6:28 PM

No active when armed output known. I can use a relay to stop the signal when the car is running by using the 12v run wire and still have continuity at rest. My problem is figuring out a relay to use in line with this one that will allow the alarm trigger wire(-) to have continuity with doors locked and no continuity with doors ulocked. The lock and unlock signal is a floating negative. I believe a latching switch is needed to control the lock/unlock relay to maintain continuity with the lock signal, but I cannot figure out how to do it . If I am unable to do it I will have to get an aftermarket alarm which will have an additonal open channel for the tailgate.

Sorry about the diagrams. They have to be printed to be readable.