Making my own Headlight Relay Harness

[bucannon]

I will have some spare time soon, so while im not home to work on my truck i figured i would make my own headlight relay harness since i have most of my electrical connectors and stuff with me.

Im have a pretty good idea of what i want to make but i dont know what measurements to cut the wires since i am 1000 miles away from my truck.

can some of yall that have made these before help me out with pictures and/or measurements of what you have. Any suggestions to help improve my harness will be helpful too.





I also found this diagram on another website:
http://www.73-87.com/7387garage/exte...ight_relay.htm


It has a decent explanation but i want the harness i make to be "plug and play" so when i go home next time i can just open the hood, plug it in, zip tie it up, and drive

[RexDodge]

I built a relay bank with headlight, electric cooling fan and fuel pump relays (and circuit breakers). I used an old license plate mounting bracket, lol. Here is a couple of pictures. Hope it helps.

[bucannon]

thats a clean install!

[memo43]

Looks like an aweosme idea, is there any way you can write up how you plan on wireing it. Im interested in how you plan on runnig the wire from the battery and which wire you plan on running where.

[Andy4639]

The wiring is pretty simple on these.
This is a typical relay wired up.
Everything is compared to diagram.
1. Run a hot wire from battery to relay #30 with fuse.
2. U will need one relay for low beam and one for high beam.
Take a test light and find the low and high beam connector on the factory wiring harnes on back of lights.
Cut the factory wiring harness about 12" from connector one wire at a time.
Ok the end of the first wire coming from the dimmer switch lets say low beam connect it to the #1 relay at #86. Then run a wire from #87 back to the light connection.
3. Now do the same for the high beam.
Cut the factory wiring harness about 12" from connector.
Ok the end of this wire coming from the dimmer switch is the high beam connect it to the #2 relay at #86. Then run a wire from #87 back to the light connection. The factory light connection has the passenger side light wire tied to it.
Then you just ground it and your done.

[bucannon]

Originally Posted by Andy4639

Cut the factory wiring harness about 12" from connector one wire at a time.

instead of doing this i would like to find a connector that i can wire up and then plug it into the factory harness once complete.


I am building this harness outside of the truck. If yall can help me determine measurements for the wires to where i want to mount the relays. also help me determine where i can find the connectors to make it "plug and play"(maybe a junkyard?)

Thanks for all the help so far!

[RexDodge]

This is the schematic I based my head light relays off of. The same as Andy's really when you look at them. The only change I made was to splice into the heavy gauge red wire that runs from the alternator to the battery. Why add another wire? It has the fusable link in it. I also opted to use circuit breakers. Simple install...just put some thought into wire routing to make looming them easy once you are done. Other than mounting the relays and circuit breakers I don't think there is much else you can do outside the engine bay. I guess you could buy the headlight plugs but it is all there for you to use. Be sure to solder and shrink wrap everything. My .02 worth...which I could not have done without the help of all the guys who chimed in to help me when I asked for help. This is a great resource for us all.

[Andy4639]

The only reason I added the extra wire is for the load. I put a bigger wire that would only carry the load of the lights on it. Plus when I did mine I never looked in this section much. I did it on my own after hearing others talk about it. Yes they are both the same final outcome with a little differant direction.

[elf w/capital T]

sweet idea rex!!

[RexDodge]

Originally Posted by elf w/capital T

sweet idea rex!!

Thanks!

[MikeyMan]

Originally Posted by bucannon

It has a decent explanation but i want the harness i make to be "plug and play" so when i go home next time i can just open the hood, plug it in, zip tie it up, and drive

I understand what you are trying to do. I will NOT be cutting any of my original wiring either. Unfortunately, I can't give you wire lenghts as your 86 will be different from my 72. It depends on how you want to route the wires, because you will have to cross over the core support somewhere to connect to both lights. (2 headlights, assuming you don't have 4 GMC)

I bought 2 new high-temp 3-prong headlight sockets. I will unplug the originals and leave uncut. I plan to tap off one of the original HL sockets to feed the relay switch side. I'll use spade crimp connectors, and just plug into the original socket. I can use the right or left socket, it depends which side is easier to mount your relay bank and tap battery power.

So: Original socket Hi & Lo jumpers to the new Hi & Lo relays switch in. 12v battery feed to relay battery in. 12v relay out through heavier gauge wires to each Right & Left, Hi & Lo through new sockets. I'll just ground the relays and third socket wire to metal, so I don't have to run all that extra ground wire.

[E.Furgal]

just an FYI.. as I'm in the middle of this..
the mid 90's full fized blazers and burbs have a 4gauge wire that runs across the coresupport from the battery to the fuse panel under the hood and has a mixi fuse holder /juction block inline
I have it wired in my truck with the maxi fuse/j.block on the pass inner fender near the battery and runs across the coresupport to another maxi fuse j. block. putting a nice thick 4 gauge wire and block near the old voltage relay. then I'm wire'n the headlights /fog light relays off that.. it's the right lenth to go from one inner fender to the other if your don't want to mount on coresupport..if mounted on coresupport you'll have a small half loop that is good for servicing it ,if you hide it down low.. mine will go behind the washer bottle and cheap.. I got mine the wire from the doners batt to fus box and alt. and two maxi fuse /j. blocks for 10.oo ,you will need to change out the main maxi fuse as it's 175 amp..
I may get another to power the rest of the truck from.. as the factory wire is mighty small..

[bucannon]

Originally Posted by MikeyMan

I bought 2 new high-temp 3-prong headlight sockets. I will unplug the originals and leave uncut. I plan to tap off one of the original HL sockets to feed the relay switch side. I'll use spade crimp connectors, and just plug into the original socket. I can use the right or left socket, it depends which side is easier to mount your relay bank and tap battery power.

Yea ive only got 2 headlights. So my understanding is that i need separate relays for Hi/Lo beams?

[MikeyMan]

Yes, 2 separate relays. One for Hi beams, and one for the Lo beams.
You then run 2 wires (one for Left & one for Right) from the Relay out (#87) for each Relay (one relay for Hi, one relay for Lo).

I bought a pair of high-temp 3-prong headlight sockets to use with the new wiring. You can figure which prong/lead is Hi/Lo/Ground by testing the original headlight socket. I'll tie in the Relay out (#87) from each Hi/Lo relay to the Hi/Lo leads on the new sockets. That way I leave the original headlight sockets and harness uncut. I'll make 2 jumper wires that will plug (spade terminal crimp connector) into one of the original HL socket to get Hi & Lo power to Hi & Lo relays at switch in (#85)

[OneOffStroker]

If you're feeling like the relay business is too stressful, go to your local pick n pull and pluck some electric fan relays from some 90's Volvos. These relays kick ass. They don't need grounded, have weatherproof connections, and are decently sized. They are for 2-speed fans, but you can use them for Hi/Lo headlights.

The big red wire on the right (30) is battery power, and use the small inputs in the middle to control the large outputs on the left. 1 goes to 1, 2 goes to 2. Super easy.

[bucannon]

Clever! I like the idea of using other factory parts(like i did in my suspension upgrade/rebuild).