Bright "AND" Dim At The Same Time Headlamp Relay Wiring

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MrMarty51

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Joined
Oct 25, 2012
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Location
Eastern Montana
First Name
Martin
Truck Year
1978
Truck Model
K20
Engine Size
400
Seems like there are a lot of questions of how to do the bright and dim at the same time headlamp mod. so the dims stay on when the brights are turned on for the quad lamp systems.
Maybe if this is good enough it could be made a "Sticky" so it`ll be easier to find for those wanting to do the switch.

First of all, I guess it would greatly help if a person understood what a relay is and how they work.
Here is a page, a simple tutorial for understanding the theory of how the automotive relay works and what each terminals job is. it is only one page with large letter writing and a few diagrams of how to wire the relay in most any application.
I would first read this before attempting to wire in Your own relay. Once the basics is understood it will take "ALL OF THE FRIGHT" out of wiring in Your own system.
One more thing, when tapping into a wire, through a splice, always stagger Your splices to keep from creating one great big knot of splices in one spot.
http://www.eurekaboy.com/f250/relay101.htm

Here is a pic. of the relay I installed on My 93. There is a lot of talk about diodes and such but just scroll down a bit and You`ll find the pics.
http://www.gmsquarebody.com/forum/showthread.php?t=5966&highlight=headlamp+diode
What I did was to tap into the bright headlamp[s wire, on the passenger side and then run a wire from the tap to where I was going to have My relay mounted, or hung.
Wire in the relay as prescribed and use the bright tapped in wire for the "Signal" wire, on the other side of the relay will be another wire run to ground.
Hook another wire into one of the battery terminal lugs and hook that, through a 20 amp fuse to the battery or + side of the relay, across the relay, from the + wire, hook that pigtail/terminal to another wire that You have run back to the headlamps wire harness and hook that wire into the "DIM" lights harness.
Now, when the headlamps are on dim, only the dim will light up.
When the headlamps are turned onto the "Bright" mode, a signal will be sent to the relay, through the switch incorporated in the relay to the ground turning the switch on.
When the switch is turned on, it will run power through the switch and back to the dim lamps bulbs turning them on while the bright lights is lit up.
 
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