Custom Headlight Harness Build

I've been looking at upgrading my headlights via the Ultimate Headlight Upgrade thread and have decided to take on making my own harness. I am going to build a harness that integrates the headlight and foglight wiring into one, has wiring for a future light bar, and that utilizes a fuse/relay box.

I ordered everything I should need off of Amazon for about $130, below is my list:

$11 BNTECHGO 12 Gauge Silicone Wire 5 ft red and 5 ft Black Flexible 12 AWG Stranded Tinned Copper Wire

10ft 12ga wire

$19 BNTECHGO 14 Gauge Silicone Wire Spool Red and Black Each 20ft 2 Separate Wires Flexible 14 AWG Stranded Tinned Copper Wire

40ft 14ga wire

$8 20 Gauge 2Pin Extension Wire, EvZ 20AWG 2 Conductor Parallel Electric Cable Cord for Led Strips Single Color 3528 5050, Red Black, 33ft/10M

20ga wire

$10 2X Female Ceramic Socket Plug Kit w/Terminals For 7” Round Lamps H4 Headlight (Yellow)

2 H4 female ceramic sockets
2 H4 male connectors

$8 Hella H4 100/80W High Wattage Bulb, 12V

2 H4 100w/80w bulbs

MUYI 2 Pcs H8 H11 880 881 Male and Female Adapter Wiring Harness Sockets Wire Connectors for Headlights Fog Lights

2 H11 male/female nylon sockets

$9 Hella 9005 100W High Wattage Bulb, 12V

2 H11 100w bulbs

$13 Dual Wall Adhesive Marine Heat Shrink - 10 Ft Roll - 1/2" Diameter - Black

wire wrap

MNJ Motor 12-Slot Relay Box, 6 Relays, 6 ATC ATO Fuses Holder Block with 41pcs Metallic Pins for Automotive and Marine Engine Bay

fuse/relay box

$12 EPAuto 30/40 AMP Relay Harness Spdt 12V Bosch Style - 4 Pack

4 relays

136 pcs Heat Shrink Insulated Waterproof Crimp Wire Connector Kit (Set Incl.-120 Heat Shrink Electrical Connectors, Heat Shrink Tube, Test Light, and Case) Connectors for Automotive & Marine Mechanics

assorted connectors
fuses

Here is my proposed wiring diagram:


The trapezoids are the adapters for the stock wiring to trigger the relays. H is high, L is low, F is fog and B is light bar. Fuses are color coded and wiring gauge corresponds with line thickness. I'm planning on running the high beams from the 87a terminal of the low relay so that I don't need separate power wires for them. Currently haven't decided if I want to trigger the highs, fogs and light bar each individually, or if I want to tie them all into my bright stalk. I am planning to ground to chassis on the driver and passenger side rather than run ground wires back to the battery to save on wire cost and harness thickness.

I'll update this thread as I build it, and hopefully it turns out awesome. Any input on what I could change or improve is appreciated!

 

Parts list looks pretty good, but I think you can do better than the Hellas for bulbs. See crashnburn80's post for the current best high wattage bulbs.

 

Hellas are hella cheap. I'm okay sacrificing a little output to save a few bucks.

 

What’s wrong with the factory wiring?

 

Not thick enough to support higher wattage bulbs.

 

That all looks very good with a few exceptions.

1. I see no need to run the high beams through the NC contacts of the low beam relay. Run the high beam relay power straight from the fuse.

2. The Headlight Services harness uses special relays with 1 input and 2 outputs. Each headlight has it’s own contact and wire to the headlight. There is no NC contact.

3. I don’t know anything about Hella, but there is no way I would spend all that effort and then install a $3 bulb. I have Osram bulbs shipped from England and I am very happy.

 

See this thread for a complete explanation of why an HD harness is required to run higher wattage bulbs:

https://www.tacomaworld.com/threads/the-ultimate-headlight-upgrade-h4-not-led-or-hid.398066/

 

1. Good point, then I could give the high beam its own fuse too.

2. I don't think this will be a problem, these relays are easier to find and running 2 wires to 1 contact should work.

3. Considering it, probably going to install the Hellas and see if I'm happy, then upgrade if I need to.

 

1 more thing, just for reliability. The low beams and high beams should be on separate fuses. That way, if you have a problem, and blow a fuse, you’re not totally in the dark.

 

https://www.rallylights.com/hella-hl87118-mini-relay-12v-40a-spst-dual-87-pin-bracket.html

 

Ooh, smart. I should look into that. Do those fit into the standard Bosch style relay holder?

 

Yes.

 

I bought my headlight harness from Rallylights and even though it’s very well made with quality components, the shipping charge was stupid expensive.

Several TW members have bought from Headlight Services and the products are just as good, or better and much more reasonably priced. Because of my experience, I will probably never buy from Rallylights ever again.

 

Fun project! Are you using standard H11 connectors for the 100w Hellas? I don't see a ceramic H11 connectors in your list, for that wattage you should really be using a ceramic H11 connector. 12 AWG will be difficult to fit into an H11 connector, but it is possible.

For high wattage bulbs, the only Hella I tried was the 130/90w which as far as low beam power is rated the same as Osram 100/90w bulbs. You can see my lux measurements at 18' below. The Hella focus was poor and peak intensity was beat by a stock wattage performance bulb, whereas the Osram 100/90w bulbs were on the other end of the spectrum. When you increase wattage, the filaments becomes larger and focus is more difficult to maintain, so while you have more light it may not be as focused and as a result not project as far. Hella doesn't actually make their own bulbs, they contract them out, mainly to Korea and China, vs Osram making their own bulbs in Germany.

For the high wattage H11s, I used 90w Flossers made in Germany. I haven't tried any high wattage Hella H11s. The stock fogs do not do a great job of cut offs though, they produce a fair amount of uplight/glare, so going with a high wattage fog bulb will produce increased glare and very bright fogs reflectors to oncoming drivers.

Cheap China relays often fail, which can lead to complete headlight failure which is a safety hazard. Hellas relays are now made in China too and do not have a great track record. I recommend using a high quality Bosch unit:

$17 Bosch 332019150 Relay

Bosch 332019150 Relay, made in Portugal.

Their shipping prices are absurd. The Headlight Services harness is far better made with higher quality components for less, which less expensive shipping.

 

The connectors I found are nylon and state they are high temperature, but I do not know what that threshold is. I could not find ceramic H11 connectors that allow you to insert your own wires, and most of the ones with pigtails seem to be 16ga.

 

https://www.summitracing.com/parts/hla-933332151/overview/

 

Ceramic H11 connectors are very hard to find, you can find them on aliexpress. Headlight plugs sells high temp connectors rated at 572 degrees with 12 AWG pigtails, the google page link lists them as ceramic but the page says plastic, though they appear ceramic. Unsure. You could probably order them without the pig tail though if you wanted to try something else that has an exact spec. You could aways use the ones you ordered and just do a test run for 30min and monitor the connectors.

http://www.headlightplugs.com/H11.ht.html

 

Silly question: our lighting system is conventionally switched. Is there any reason to run a ground wire back to the headlight connector in terms of the part of the circuit that will be triggering the relay?

For example, to trigger my high beam relay, should I run a hot wire from the OE connector to the relay, and then a ground from the relay back to the connector? Or does it not matter whether I ground back to the connector or just ground to chassis?

 

The relay to the headlights & fogs are not "conventionally" switched.
For the ground use the bolts already available on either side of the engine room.