'96 GMC 1500: need suggestions for routing HD headlight wrg. harness + 4Hi wiring in rad area...

[DennisT]

Putting together my composite to quad sealed beam headlight conversion, for my 1996 GMC 1500. Lots of info around here, but I'd be interested in how some of you routed your new wiring. I'll be mounting my accessory fuse block and 3 relays on inner fender next to battery. Not a lot of room, but I'd like the positive hot direct headlight wiring to have a very short run to their fuses from the battery. I am trying to decide how to run new 12ga. direct headlight feed wiring, in split-loom over to driver's side. You would think there would be a lot of room under that hood, but there isn't. Options seem to be on the motor fan side of radiator, forward and in front of the rad, above rad or below rad. I'll use the passenger side factory original headlight connectors as trigger wires for relays. I'll weather cap those abandoned in place headlight connectors on the drivers's side, but leave in place. I've wired in relay-activated lights before, but not like this with a third relay for 4HI. I have a rough schematic/diagram, but wish I had a better one. Thanks for experience tips, Dennis

 

[langkg]

Putting together my composite to quad sealed beam headlight conversion, for my 1996 GMC 1500. Lots of info around here, but I'd be interested in how some of you routed your new wiring. I'll be mounting my accessory fuse block and 3 relays on inner fender next to battery. Not a lot of room, but I'd like the positive hot direct headlight wiring to have a very short run to their fuses from the battery. I am trying to decide how to run new 12ga. direct headlight feed wiring, in split-loom over to driver's side. You would think there would be a lot of room under that hood, but there isn't. Options seem to be on the motor fan side of radiator, forward and in front of the rad, above rad or below rad. I'll use the passenger side factory original headlight connectors as trigger wires for relays. I'll weather cap those abandoned in place headlight connectors on the drivers's side, but leave in place. I've wired in relay-activated lights before, but not like this with a third relay for 4HI. I have a rough schematic/diagram, but wish I had a better one. Thanks for experience tips, Dennis

Apparently we’re both in a parallel world as I’m doing exactly the same thing. I assume you mean the HD harness one of the forum members sells.

I’m installing on a ‘94 and battery is on passenger side. I assume that’s the same on a ‘96. It never even occurred to me that you could probably run it “backwards” meaning putting the relay box near the battery and shorten up the power wire.

I was figuring out how to run the power wire yesterday evening and came to a similar conclusion that along the top of the core support was probably my best bet.

I guess I should think about it some more but it seems like you could run it “backwards” so to speak

Was just getting ready to drill some holes in the driver side fender to mount the relay box but stopped there.

 

[PlayingWithTBI]

Here's what I did on my 88 for the relays and a schematic I drew up for the 4-High mod. HTH

Electrical Upgrade? Just do it!

I was looking under the hood of my truck and decided the Mickey Mouse wiring I did for my sub woofer and A/C compressor coil looked like crap. If I wanted to do a "4 Hi" mod or add something else, it'd get even more congested. You can see here the way I tapped the in-line fuses and mounted the...

www.gmt400.com

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[DennisT]

langkg, thanks for the tip. Although since I had almost all the materials, I'm making my own harness. Not sure what you mean by, "running backwards." My thinking, (which is not always right), is that if I locate my new fuse block and relays adjacent to the battery, have short runs for that portion, then the long runs will be two, (low beam and high beam), for the pair of lights on the driver's side. I think I only need to pull trigger leads from my truck's original headlight feed right below and inside of the battery area. I need to look closely at your thought of running crossover wiring over the radiator core support. If nothing else, it keeps it up higher to install.

tbi, that looks to be a good diagram. I appreciate that as it covers the gaps in my other diagram I found within these forums. Sure seems to take care of heavier battery feed to headlights, but inserts 4 HI at the same time.

Two good replies.

 

[langkg]

Hi DennisT
I got my harness from 5vortec7 and he replied to me on another thread that it designed for the relay box to mount on driver side and power wire runs across firewall to power distribution block on passenger side.

He did indicate that you could mount it close to battery and run the harness from passenger side to driver side (what I referred to as backwards).

I need to look at it some more and make a decision. I have my Holley Hyperspark box mounted to passenger side fender already so space is somewhat limited for me there. I’ll probably mount on driver side in front of wiper fluid tank as he intended although that’s more wire on an already crowded firewall due to sniper and Hyperspark

 

[DennisT]

I'll be interested to see how everything goes together for you. I have a lot of interruptions in life, so things here go slow. I'm going to build headlight side of 12 ga. wiring first so I can get the headlight assemblies in place with wire connectors already attached. Hopefully I'll have all the primary routing figured out by then. I'm putting in a new grill and if I do things this way, maybe I can have all the grill work done and just finish working inside the engine bay for final wiring.