Dome light + Trigger tied?
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=48383
Printed Date: July 05, 2025 at 12:28 AM
Topic: Dome light + Trigger tied?
Posted By: Eclipse71985
Subject: Dome light + Trigger tied?
Date Posted: January 23, 2005 at 11:55 AM
can the (-) dome light and (-) trigger from the alarm be tied to the dome light of the car without trouble? This is the only thing that I THINK could cause a problem because the alarm would make a ground connection to turn the dome on and the alarm see the ground and sets the alarm off right? I'm not sure I think I'm just looking into this too much.
Replies:
Posted By: KarTuneMan
Date Posted: January 23, 2005 at 12:44 PM
Think about it like this......when is the ONLY time your gonna turn on the dome light............................................................................................................................when you disarm and unlock the doors.  -------------
Posted By: auex
Date Posted: January 23, 2005 at 12:49 PM
If that is what your car calls for then yes. This is very car dependant.
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Posted By: Eclipse71985
Date Posted: January 24, 2005 at 2:59 AM
Well this is the whole problem. I got an alarm setup because I am ok with with anolog and digital electronics (I went to a trade school) and with auto (learned from my father) so I gave it a shot. I hooked it all up with a combo setup locks remote start and alarm, and it all worked...but, when I went adjust the shock sensor by setting the alarm off by hitting the truck I let the alarm run its cycle a few times and it died slowly until the horn took over and thats all that sounded. Now I went over everything again and again and the only thing that I think could cause conflict is that the alarms dome and trigger are tied togeather. And because one creates and the other recives thats this only possible thing I can think of besides defect. I think when the alarm sets off the dome flashes as well. BTW the truck is a Ram 1500 01.
Thanks for the input so far.
Posted By: Eclipse71985
Date Posted: January 24, 2005 at 6:10 PM
I guess my question is Do I need to use diodies for that? None of the install notes mention to use a diode, just doom is same as door trigger.
Posted By: metaverse
Date Posted: January 24, 2005 at 7:32 PM
Well..some cars have the dome light circuits tied into the door lock circuits.. I.e. when the door locks unlock, the dome light comes on automatically. I can tell you that on mazda protege's, they are wired this way. I don't even bother hooking up the dome light supervision wire in those cars..works everytime.
As for the dome light and door trigger interfering, I cannot see how. The door trigger is an input line.. the dome supervision is an output line..I'm talking alarm wires..not car wires. I can understand where you think a dome light wire comes on to feed the door trigger wire and trigger the alarm. The only time a dome light comes on besides the factory design is when you unlock a car (it sends a signal to the dome light wire to turn on) or the alarm goes off, it flashes the dome light to attract attention.. When you hit disarm on the alarm keyfob, the priority is always to disarm the sensors, unlock the doors (if programmed) and turn on the lights (if programmed) The design of aftermarket alarms always computes a couple of milliseconds to send a pulse on the dome light wire.. Use a meter to verify what I'm talking about..or even watch the dome light activate delayed a bit after disarm. I have never seen a dome light interfere with a door trigger.
You can diode isolate, or better, relay activate the dome light wire..Gives you a bit more delay with the relay in circuit.. Put a 1amp diode with the silver band facing the car side on the door trigger wire..basically the silver band is facing away from the alarm brain. Wire up a relay with pole 85 to the alarm dome trigger wire, pole 86 to fused 12v, pole 30 to body ground, and pole 87 to the car dome trigger wire. Btw, check your grounding points for your alarm.. a weak siren usually means a poor or no ground..
Posted By: Eclipse71985
Date Posted: January 25, 2005 at 5:12 AM
My main concern was that on the alarm I had both the trigger and dome light wires tied togeather and the trigger from the alarm would input from the dome from the alarm and cause the troubles I had with with the unit. The more I think about it seems less likly that and just a defect. The siren was not weak it made that dieing sound thats hard to replicate by writing, kind of like a cop car in a movie when it gets totaled :lol: if that can give an ideal of what I'm talking about. All my grounds are 100% and I did check again but what made me think it was fried was that the horn sounded only the unit did not respond to remote and the led went dead.
Posted By: CBill
Date Posted: January 25, 2005 at 6:50 AM
Most alarm dome light output are limited to 100mA-200mA and some instruction will even tell you if it only limited to this mA and dome light draws a lot more amprage than that so you will have to use a relay switch instead. Basically you would connect the domelight wire from the alarm to the coil of the relay switch and the other end of coil to the 12 volt postive (most dome light alarm are ground outputbut if your postive then other end to the ground) and both switched contact points to domelight switch in the dashboard or at the keyless module if you vechile have one. Bill
Posted By: Eclipse71985
Date Posted: January 25, 2005 at 12:27 PM
I will check the current its drawing but I don't think its much and even the wire is very small. I do not have a keyless module and it is - for the dome. But is it ok to have the trigger tied with the dome on the alarm then goto the dome wire on the truck if its low current? Or do I have to use diodes or relays with diodes? I'm starting to think its too much trouble for a stupid dome light and just lose it and only keep it for the trigger. And I thought the dodge 5-wire locks was going to be the big problem. :lol:
Posted By: CBill
Date Posted: January 25, 2005 at 3:12 PM
You have to use relay if the instruction say that the dome supervisor light is only 100mA-200mA but all alarm system are different however most alarm system only allow 100mA - 200mA output on dome supervisor wire. Dome light draws much more current than 200mA and you will burn out the tranisitor inside the alarm system if you let the dome light draw current from it if don't use the relay and the instruction calls for the wire to stay under 200mA Just read what your instruction tells you to do .. Here an picture from wirewerx site showing how to connect using relay .. .. Like I said connect the dome supervisor light to the coil of the relay #86/85 then the contact points #87/30 are connect to the ground and the door switch if it a grounded switch type .. 
Bill
Posted By: CBill
Date Posted: January 25, 2005 at 3:18 PM
I want to add that you must check for if the dome supervioring light is either negitive or postive output .. so you have to hook up the relay depending what output it is .. the picture above I saw whoever did the picture use postive dome light out .. so it just depend on what your alarm system instruction calls for but still if it says it's less 200mA out then you need to use a relay switch .. Bill
Posted By: Eclipse71985
Date Posted: January 26, 2005 at 8:33 AM
As I posted before it is neg. the instructions for the alarm tell me nothing else but that it is -. And the wiring information say nothing as well. Only that the headlights are high current and need a relay but dome and park are ok.
Posted By: Jschult3
Date Posted: January 26, 2005 at 3:42 PM
What type of alarm? What type of Car? ------------- Jeff
Always Verify Wire information before Connecting! Just a Darn Good DIY'R
Posted By: Eclipse71985
Date Posted: January 26, 2005 at 5:51 PM
generic combo off ebay why I think it was a defect. I am just trying this out for the first time to see how hard it is so I went cheap.
Ram 1500 2001 no factory alarm
Posted By: Jschult3
Date Posted: January 27, 2005 at 2:02 PM
Dodge generally uses a negative door trigger system. As long as your alarm combo uses a neg domelight wire you'll be fine. The domelight will only come on after disarming when the alarm will ignore a neg feed on the wire. Basically what your doing is tricking the car into thinking you left a door open. 30 seconds later the alarm tells the car you've closed it. What you want to do is connect the relay like this, you will need one in most situations and it's better to be safe than blow up a circuit on the main alarm pad. 85=+12 volts constant 86=Domelight wire from alarm. 87=Connects to the NEGATIVE domelight wire in car 30=connects to ground 87A=not used. Connect the neg door trigger from the alarm at any point on line 87. This way when the domelight wire comes on from the alarm the relay turns out and connects pin 30 to 87. This applies ground to the circuit and turns on the domelight. The Door trigger wire can be connected anywhere down line of pin 87. This way if someone opens the car and the NEGATIVE wire turns on and the alarm see's negative currnet which sets off the alarm. So to answer your question, YES, the door trigger and domelight in this vehicle should be connected. Be sure to meter your wire to verify the wires are negative. If they're positive triggered email me an dI'll tell you how to fix. Good Luck ------------- Jeff
Always Verify Wire information before Connecting! Just a Darn Good DIY'R
Posted By: Eclipse71985
Date Posted: January 28, 2005 at 7:11 AM
I am using the negitive wire I had it all working before it blew and I will be getting another feb. 1. I will do this once I recive the alarm. I guess having the trigger and dome tied isn't a problem seeing how they will come into contact how thats setup. I really think it was just a defect now but I will still do it this way becuase it looks more professional and is safer just in case I am wrong.
Thanks for all your help guys I hope when I try this on my car with a better system it will go smoother than on this truck.
Posted By: CBill
Date Posted: January 28, 2005 at 9:08 AM
Your going to blow another one if you don't use a relay switch for your dome supervisor light trigger .. Bill
Posted By: Eclipse71985
Date Posted: January 28, 2005 at 7:19 PM
Yes I am going to wire it like you and Jschult3 are telling me.
85=+12 volts constant
86=Domelight wire from alarm. (negative output)
87=Connects to the NEGATIVE domelight wire in car
30=connects to ground
87A=not used
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