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Dome Light Supervision vs. Negative Door Trigger

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=9237
Printed Date: September 12, 2025 at 3:24 AM


Topic: Dome Light Supervision vs. Negative Door Trigger

Posted By: buys-a-lot
Subject: Dome Light Supervision vs. Negative Door Trigger
Date Posted: February 08, 2003 at 4:59 PM

Hi,

I'm very, very stuck.  I'm installing an Omega 3.0 on my 1995 Toyota 4runner, and I just can't figure out what to do with the "dome light supervision" and the "negative door trigger".   Are they one and the same?  All the references I've seen say they are both a BLACK/ black white wire on the top of the fuse box.  I've found the wires (one is black, and one is BLACK/ white) and I don't know which one to connect to the dome light, and which one to connect to the door trigger.

I'm just lost. . .Help if you can.

Sincerely,



-------------
Russ



Replies:

Posted By: ossrom
Date Posted: February 08, 2003 at 5:37 PM

the black wire is constant (+),

the BLACK/ white is the one that turns to ground (-) when a door is open, therefoere this will be your door trigger.

if you want to use dome light supervision from your alarm yu will need a relay, wired as follows;

87: ground(-)

86: constant power(+)

87a: no conection

85: to the alarm's domelight sup. wire

30: to the domelight wire in the car (BLACK/ white stripe)

hope this helps



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ossrom




Posted By: Chris Luongo
Date Posted: February 08, 2003 at 5:38 PM

Some cars get complicated----- many have built-in domelight delay.  Or for another example, the BCM (Body Computer Module) in many GM cars, puts the domelight circuit "to sleep" after 20 minutes of inactivity---which makes a false alarm.  In cars like these, we try to avoid going directly to a domelight wire for door trigger, but rather, find some other wire that is not affected by these issues.

On cars like that, sometimes the true door trigger wire will also turn the domelights on if we ground it----and sometimes not.  As you can see, an installer might find a true, delay-unaffected source for the alarm's door trigger----but at the same time, he'll go right to the domelight wiring to do domelight supervision.

Your 4Runner is very simple, electrically speaking.  The domelight is not affected by the car's computer, and it doesn't even have any delay circuitry.  Therefore, as far as your particular installation is concerned, "door trigger" and "domelight supervision" are one and the same.

If you look closely, you'll see that the two-pin plug at the top of your fuse box simply runs toward the A-pillar, up along it, and then across the roof toward the domelight------one wire is constant positive power, and the other one gets a ground whenever a door is opened.  Also, if you close all the doors, but then apply a ground to the wire, the domelight will turn on.  (Still, though, you must leave the overhead light's control switch in the "door" position.)

Your alarm's "domelight supervision" output is designed to turn on the domelight upon disarming, so that you can look inside for carjackers, find your car keys, and so on.  Some alarms also turn the light on right as you shut the car off, and others will flash the domelight on and off during a breakin, to attract more attention.

If you don't care for this feature, simply leave the wire unconnected.

If you do want it.....your alarm may have two types of outputs:  low-current or high-current.

If it is low-current (it'll say something like 300mA max.), you'll need a relay----the output from the alarm triggers the relay, and the relay supplies a strong ground to the car's domelight.  This site has excellent descriptions of how relays operate, or the alarm's install manual might include instructions on this.

Some alarms have their own domelight supervision relay built in-----in this case, it'll have two wires, labeled input and output.  Tie the input to ground, and the output to the car's domelight wire.





Posted By: buys-a-lot
Date Posted: February 08, 2003 at 9:39 PM

Thank you so much!!  I can't begin to tell you how helpful that has been!  Thanks thanks thanks!



-------------
Russ





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