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How to turn on dome light with negative trigger

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=141239
Printed Date: April 29, 2024 at 11:51 AM


Topic: How to turn on dome light with negative trigger

Posted By: modeladave
Subject: How to turn on dome light with negative trigger
Date Posted: May 02, 2016 at 1:28 PM

I'm building a car and looking to hook up interior dome lights that go on and off as the doors open or close and want to use relays. The power windows use a set of 4 door contacts, of which some are grounded when the door is closed. When door is open they are all an open circuit. Rather than put in a door switch for the dome lights, I want to tap into a door contact and use it to switch continuity of a negative.

Door Open, no continuity, dome lights go on
Door Closed, continuity, dome lights go off

Its kinda backwards to how relays work I think. Any ideas how to wire this up? I didn't want to run +12V all the time between 85 and 86 terminals of the relay but I'm thinking its the only way. I'm stumped.

Appreciate the help.

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Thanks in advance,

-coupster



Replies:

Posted By: howie ll
Date Posted: May 19, 2016 at 11:39 AM
If those wires are grounded only when door is closed you've got continuity problems with your wiring, also means the power windows would be unusable with a door open!
Either door switches or a micro-switch on the unlock rod going to ground (that's how it's done OEM)

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.




Posted By: howie ll
Date Posted: May 19, 2016 at 11:40 AM
You could also use a PAC Tr1 or DEI 528T as a timer, triggered by ignition off.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.





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