Relay for power

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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=47127
Printed Date: May 11, 2025 at 8:47 PM

Topic: Relay for power

Posted By: drsnoze
Subject: Relay for power
Date Posted: January 07, 2005 at 8:07 AM

I’m not sure if I have completely grasped the concept of this relay thing.
I have two blue lights for my truck and the problem I have is that they have power constantly to them. I want to use a relay to give them power only when the ignition is on.

86 12v ignitions
87,87a 12v output to blue light (only get power when ignition is on)
85 ground
30 constant 12v

If that is incorrect please help me

Replies:

Posted By: KarTuneMan
Date Posted: January 07, 2005 at 11:26 AM

You dont need to use 87a most would wire it like this

87 gets 12 volts fused (enough to hadle the draw of your lights)

86 to ground

85 gets your ign. trigger

30 goes to the lights They, like you want will only come on with IGN. it's basically the same as your description......just Im used to "looking" at a relay from a certain side. If you do it wrong....it just won't work

FUSE IT!!!

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Posted By: drsnoze
Date Posted: January 07, 2005 at 1:34 PM

ok so
87 is constant 12 volt (fused?)
86 ground
85 12 volt ignition
30 to blue lights (?)

i should fuse the constant not the lead from the relay to the light?

Posted By: auex
Date Posted: January 07, 2005 at 2:39 PM

That will work. And yes fuse the power going into the relay.

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