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Headlight Relay Build

 
  #1  
Old 02-01-2015, 01:55 PM
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Headlight Relay Build

I finally got my headlight relay setup finished, so I thought I would share it with everybody.







This was the first version. I built 2 identical ones, one for each side. Then I thought, "You dummy! One box will be more than enough to run both sides!" So the second is up on the shelf for the next truck.



I didn't like the big red power wires. They were just to much. So I made the power connector like this to save space and hold the relay in place. In the process of building that, I realized it needed a fuse or relay somewhere. I had a relay in the drawer with a place for a fuse. It came off of one of our tractors. So I made this:




That looked like it would work well, so I ordered some from John Deere. They were only $8.20. Surprisingly inexpensive.



Relays came in today.



Replaced the fuse with a circuit breaker.

Here are a few pics of the part# of the relay.







And then I looked at the instructions. The power terminal is in a different location! Aw crap!







Ended up making 3 versions before I got it right.



I ordered this wiring connector. It allows me to simply unplug the original plug from the light bulb and plug it to the relay box. Then plug the relay box plug onto the light bulb. If I should happen to have a relay failure, all I have to do is unplug and replug and I'm back to factory stock till I can fix it.





Color coding made easy! Factory colors and all!



For the power to the relay box, I tapped into a resettable circuit breaker over by the battery. Lights don't need 100 amps, but the power will be going back out of that relay box to future projects, so that's why I did it that way.



Power and ground in loom tucked in behind the radiator.



Box is wired. Power and ground in. Plug from original harness coming in and 2 plugs going out to the headlights. The one going back to the other side of the truck is also tucked behind the radiator.



Installed and done!



Now granted, a simple relay and plug like these with an inline fuse or breaker would be just as effective and properly placed would look good too. But there's nothing quite like trying to re-invent the wheel. Hey, if it's worth doing, it's worth over-doing, Right?!
 
  #2  
Old 02-01-2015, 02:14 PM
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Good job! Trial and error pays off and you got it right. How about a "How to" write up? I'm interested in putting a relay in at some point, but I really don't know how to go about it.
 
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Old 02-01-2015, 03:13 PM
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The simplest setup is the last pic. Most of the "how-to" is on the relay package itself. You need 2 relays, one for hi beam and one for low beam. The posts on the relay are numbered.
#30 is power from the battery. This is where you will want a circuit breaker of 10 amps per relay.
#85 is ground. Make sure you have a really good to-the-battery ground. Poor grounds generate heat in the circuit and burn stuff up.
#86 will come from either the low beam or hi beam wire FROM THE TRUCK.
#87 will go to either the low beam or hi beam BULB.
Double up on the ground on the bulb connection and the original ground wire going back to the truck. You can combine them with the ground #85. You can never have too much good ground.

And really, that's about it. A new plug for the light might not be a bad idea, they are cheap. Good heat shrink type connectors work well and are dependable. A little dielectric grease for the plug connections won't hurt.
 
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Old 02-01-2015, 03:40 PM
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I made a couple up for my trucks with four relays to run the plow lights also. 2 relays are all you need for both sides. Ive seen a couple relays that were hanging upside down fill up with water, do i made sure to mount them upright. There is a writup in the stickies in the 80 - 86 section.
 
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Old 02-01-2015, 04:53 PM
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Smile

Wow, much tidier than mine. Back to the drawing board
 
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Old 02-01-2015, 05:36 PM
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My relays are a mess compared to that, nice work!
 
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Old 02-01-2015, 05:54 PM
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Nice job on the setup. I have the RJM relay harness. Its the nicest premade one I've seen.
 
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Old 02-01-2015, 06:26 PM
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Thanks guys!
 
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Old 02-02-2015, 12:13 AM
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Couple questions if you don't mind.

What circuit is fused with that JD relay? I hope it would be the common contact (30 on a Bosch relay). Neat part!

Also looks like the instructions suggest 30 and 86 are transposed. So this means the JD part is not standard Bosch relay wiring?



What did you use for a box and the terminal strip?
 
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Old 02-02-2015, 06:34 AM
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Power coming out of 87 is what is fused by the relay. On my setup, power going to the relay (30) is circuit breaker protected up the line and switching power coming in to the relay (85) is fuse protected by the original fuse for the headlight switch.
Yea, JD used to use Bosch and Hella relays, but now they use something odd. I will check the brand and post it.
The box is a junction box used for trailer light hook ups. I use them for all kinds of stuff. Cheaper than an electrical project box, has in and out holes with grommets, mounting flanges, water tight, and a stud strip.
 
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Old 02-02-2015, 08:23 AM
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I am thoroughly confused

Why do you have more than 2 relays?

And what is with the junction boxes?
 
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Old 02-02-2015, 11:55 AM
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Thanks for sharing!

Where did you get the nice box for the relays and the buss-bar?

That's a nice looking box. Seal it all up and protect everything from the salt and corrosion.
 
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Old 02-02-2015, 07:19 PM
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Originally Posted by Diesel_Brad View Post
I am thoroughly confused

Why do you have more than 2 relays?

And what is with the junction boxes?
There are only 2 relays in the box. One runs BOTH hi beams and the other runs BOTH low beams. The junction box and buss bar are to join everything together and protect it from moisture and dirt. Probably overkill but hey, if its worth doing it's worth overdoing, right?
 
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Old 02-02-2015, 07:22 PM
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Originally Posted by warren561 View Post
Thanks for sharing!

Where did you get the nice box for the relays and the buss-bar?

That's a nice looking box. Seal it all up and protect everything from the salt and corrosion.
The junction box is commonly used on trailer wiring. Mine came from the local trailer place. Ebay has plenty of cheap ones and etrailer has a good selection also.
 
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Old 02-02-2015, 07:26 PM
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Originally Posted by eakermeld View Post
There are only 2 relays in the box. One runs BOTH hi beams and the other runs BOTH low beams. The junction box and buss bar are to join everything together and protect it from moisture and dirt. Probably overkill but hey, if its worth doing it's worth overdoing, right?
O, you made 2 sets. for 2 trucks. I was really thrown there
 

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