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post #1 of 48 Old 06-13-2009, 12:19 AM Thread Starter
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Headlight harness how-to

Ok so I just got done doing this and had help from John L, Paragon and others but here's an attempt at a step by step.
First of all why would you want to replace a perfectly functional factory harness?
Well, if you use a good gauge wire and dedicate a run to the battery with it, you'll get more power with less voltage drop, makes for brighter lights.
You also remove the computer nanny and can run higher wattage bulbs without the canbus stepping in and become the can't bus, cutting your power.
Of course higher wattage bulbs may not be legal and won't last as long.
Simply running relays and triggering them off of the factory harness won't work because the stock headlight power is pulse width modulated and will cause your relay to flicker and drop out, thats where the capacitors come in, and the diodes keep from backfeeding to the computer.

I'm also basing this on upgrading Delta lights - the only real difference is Delta provides a harness to adapt over to a H4 bulb.

Parts list -

about 12 feet of 10-12 gauge wire to run from battery to passenger side headlight and from light to light for the positive leads
2 30-40 amp 12v relays
2 100uf 35v electrolytic capacitors
2 1N4001 diodes
all available at radio shack

You'll also need a 40-50 amp fuse and holder or circuit breaker available at most autoparts stores.

This is probably gonna be kinda confusing so you may wanna read it a few times.
I ran the 10G wire from the battery up to the passenger side headlight area, install the fuse within a few inches of the positive connection to the battery
split this to run to the supply side of the relays (terminal 30).
you'll use 1 relay for hi beam, one for low
I took driver side adapter harness and cut it about 2" from the jeep side plug and used the wires on that side to wire the relays and the rest of it to wire the headlight.
You can get your hi and low beam triggers and your ground for the relays from the 3 wire, jeep side portion of the adapter harness.
you can split the black ground from the jeep side harness to the 2 grounds on the relays (terminal 86).
the yellow wire will be the positive relay trigger for your low beam relay
the blue wire will be the hi beam trigger (terminal 85)
then the switched output terminal (87) splits to feed the corresponding wires in the lightbulb harnesses ie the output wire from the low beam will tie to the yellow wires to the bulbs, the output from the hi beam relay to the blue wires of the bulbs, the grounds from both bulb harnesses goto the chassis for a ground.
I used a factory ground point above the passenger headlight for that side and a body bolt on the driver side.
Make 2 10G runs to feed the drivers side, cut that adapter harness, ground the black and splice the positives coming across to the hi and low beam positive wires.
That takes care of the wiring, but if you stop here you'll get flickery funkiness.


Wire a capacitor across the positive and negative coil triggers on the relays - this smooths out the power and prevents the flickering. ,Make sure you wire the polarity on the capacitor correct, positive to positive, ground to ground.

The diodes may or may not be needed, but they are cheap protection for the computer.

The diode goes between the positive relay trigger wire - from the jeep side harness and the positive trigger on the relay. The band side of the diode goes toward the relay.

That's it!

Canbus is bypassed and full power to the lights.

I hope this makes sense!
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post #2 of 48 Old 06-13-2009, 01:21 AM
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This diagram confuses me

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post #3 of 48 Old 06-13-2009, 01:37 AM Thread Starter
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what specifically confuses you?
I'll try to help if I can

cliffs notes version:

2 relays - 1 for hi 1 for lo beams
stock headlight wires to trigger and ground relays
capacitor across the stock wires (pos & neg) that run the relay coils
diode in line with the stock positive wire between the relay and the jeep
headlights take 3 wires, 1 common ground, 1 hot for low beam, 1 for high
ground the lights to the chassis, feed the hots off the relay outputs


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post #4 of 48 Old 06-13-2009, 09:29 AM
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Quote:
Originally Posted by j-sack View Post
This diagram confuses me
Here is the orginal I posted a couple years ago.


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post #5 of 48 Old 04-14-2012, 08:11 PM
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Can we get some pictures? I always hate looking at wiring diagrams. Real pictures will help make it "click" for me. Thanks.
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post #6 of 48 Old 09-22-2012, 07:05 AM
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bump as this is the easiest and perfect way to get rid of headlight flicker with aftermarket units. Venom did a HUGE favor by making this suck much less to figure out. all items are easily found at radio shack.

some hints: using an axial instead of radial capacitor is easier to install. axial has the leads at each end and radial has both leads at one end. using an axial cap allows you to work "in-line" and heat shrink everything easier.

also again the ARROW on the capacitor should go to ground.

and again, the LINE end of the diode goes to the relay.


I found if do all the diode/cap part first then it would be less confusing to a novice.
Like this: connect your new low beam switching wire to the factory wire, cut your new low beam switching wire a few inches after that, solder in the non striped end of the diode to that lead, solder your low beam wire to the striped end of the diode, heat shrink it and move on. repeat for high beam

a couple inches after your "inline" diodes go and strip a 1/4-1/2 patch on your new high/low beam switching wires, wrap the NON ARROW lead of the capacitor around that bare wire (one cap per), solder and seal. then go and strip a patch on your ground wire, twist both arrow leads of the cap together, wrap them around the exposed ground wire, solder and seal.

now you have just your normal wires to work with instead of trying to solder caps/diodes to your relay base a switching wire for high and low and the ground for the relays
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post #7 of 48 Old 09-23-2012, 12:03 AM
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Quote:
Originally Posted by dsy View Post
Here is the orginal I posted a couple years ago.

Yeah this is the one I found and used a couple of years ago. Thanks for putting it out there way back when

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post #8 of 48 Old 09-23-2012, 12:50 AM
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A couple of notes.

First of all, I find it easier and more reliable to solder the capacitor and diode to the pins on the relay socket before inserting them into the socket. If your socket came with the pins pre-installed with pigtails on them, it is easy to get them out by sliding a jewelers screwdriver to gently release the little tab that locks them in place. This is also handy for replacing the 14 AWG wire with 12 AWG on the load-carrying contacts.

Cover the entire cap and diode with marine heat-shrink tubing (has adhesive inside that melts to create a water-tight seal) then glue to the bottom edge of the socket to keep them out of harm's way.

Also, if you look around you can find power relays with diodes built-in. You don't have to use standard Tyco-style automotive relays, anything that is waterproof and rated properly will work. You can also find relays with resistors built-in. The resistor will attenuate any spikes coming out of the relay coil instead of blocking it entirely, which probably safe enough (industry standard) and should result in quicker relay operation (no 0.7 voltage drop across the junction). Look at ISO 280 mini and micro relays for ideas.

10 AWG wire is a little overkill IMO, and will be difficult to get into the relay socket and much more difficult to solder. Keep your runs as short as possible, should be less than 10' from the battery through the relay to both lamps, and 12 AWG should be fine and is easier to solder and fit into the relay socket.

To help keep your overall wire run as short as possible, run the ground from the headlamps separately to the nearest ground stud instead of running them back to the battery. The battery negative terminal is strapped to the frame and the chassis making a very large conductor, much larger than any wire you could reasonably connect to the headlights.

Using different color wire makes completing your connections and future troubleshooting/repair much easier. This is even more important when you're building a full wiring harness for additional lighting along with your headlights. You can tag or mark the wires but that tends to wear off over time and doesn't help if you need to break-open the middle of the harness for some reason.

DSY's drawing specifies a 220pF cap. Venom's specifies 100uF, which is considerably larger. The larger the capacitance the lower the relay will trigger. I forget which value I used, but I suspect it was 100uF because there is a noticeable delay in switching over from low to high beams and back. Of course the computer-controlled switching itself is already laggy, but now even worse. Very frustrating when you're trying to flash your brights a few times as a hazard warning to oncoming traffic. Note that you don't have to completely eliminate the CANBUS modulation, just attenuate it enough so the voltage doesn't drop below the relay's unlatch voltage, which if I recall correctly, is somewhere around 2.2V.

One of these days I'm going to actually take my scope out and measure the CANBUS modulation myself. But I think that if DSY was successful with 220pF there should be no reason to go larger, and good reason to not.

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post #9 of 48 Old 09-23-2012, 06:22 AM
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Quote:
Originally Posted by BumpInTheRoad View Post
DSY's drawing specifies a 220pF cap. Venom's specifies 100uF, which is considerably larger. The larger the capacitance the lower the relay will trigger. I forget which value I used, but I suspect it was 100uF because there is a noticeable delay in switching over from low to high beams and back. Of course the computer-controlled switching itself is already laggy, but now even worse. Very frustrating when you're trying to flash your brights a few times as a hazard warning to oncoming traffic. Note that you don't have to completely eliminate the CANBUS modulation, just attenuate it enough so the voltage doesn't drop below the relay's unlatch voltage, which if I recall correctly, is somewhere around 2.2V.

But I think that if DSY was successful with 220pF there should be no reason to go larger, and good reason to not.
My set up has been working perfect from day one when I put it together
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post #10 of 48 Old 09-23-2012, 10:06 AM
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My set up has been working perfect from day one when I put it together
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How did you come up with the value for the capacitor?

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post #11 of 48 Old 09-23-2012, 10:27 AM
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How did you come up with the value for the capacitor?
Buddy of mine is an electrical engineer. I told him what I wanted to do and that was the value he suggested.
It worked great so I saw no reason to change it.

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post #12 of 48 Old 09-24-2012, 11:54 AM
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I have a 2011 with Hella H4 which is the default headlights from Jeep here in Sweden.

And if I replace the OE wiring harness to be able to run the headlights with non fluctuating power wont that trigger the TIPM to think that the headlights are bad (since they are not drawing any/little power) and raise a warning light on the dash?

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post #13 of 48 Old 09-24-2012, 12:02 PM
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Quote:
Originally Posted by jronnblom View Post
I have a 2011 with Hella H4 which is the default headlights from Jeep here in Sweden.

And if I replace the OE wiring harness to be able to run the headlights with non fluctuating power wont that trigger the TIPM to think that the headlights are bad (since they are not drawing any/little power) and raise a warning light on the dash?

-J
The PCM (not TIPM) will record DTC's for the high and low beam lamps that are left disconnected. But, at least on the US versions, no dash warning is displayed.


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post #14 of 48 Old 11-06-2012, 08:20 AM
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So I'm bringing this back from the dead. I can NEVER get ahold of danial stern so I am going to go with deltas and make my own harness. My one question is how are you tying the factory harness into the new harness? Are you cutting the factory harness or using some sort of adapter that plugs into the stock harness and just has backed wires on ethe other end. Thanks.
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post #15 of 48 Old 11-06-2012, 07:50 PM
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So I'm bringing this back from the dead. I can NEVER get ahold of danial stern so I am going to go with deltas and make my own harness. My one question is how are you tying the factory harness into the new harness? Are you cutting the factory harness or using some sort of adapter that plugs into the stock harness and just has backed wires on ethe other end. Thanks.
I just used scotch taps to tap into the passenger-side headlight harness and then wrapped them overall in self-sealing rubber tape to keep them dry. There's very little current needed to activate the relays. If you want to leave the OEM wiring intact you can order an H13 Male connector off eBay for around $6.

I suggest putting the 1N4001 diodes as close to the OEM wiring harness as possible. These have a maximum current rating of 1A and so will pop like a fuse in the event you ever get a short between the OEM harness and your relay, protecting your wiring.

Don't forget the 220pf 35V capacitor across the relay coil terminals to filter out CANBUS modulation and prevent relay chatter.

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post #16 of 48 Old 12-07-2012, 11:25 AM
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I know this is an old thread, but I have a question that I think is worth bringing it back. I understand the wiring diagrams - thank you very much for them Venom! I would like to purchase the harness already assembled for my JK. Who can I talk to about getting this done?
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post #17 of 48 Old 01-01-2013, 01:54 AM
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Originally Posted by atmotocrosser View Post
I know this is an old thread, but I have a question that I think is worth bringing it back. I understand the wiring diagrams - thank you very much for them Venom! I would like to purchase the harness already assembled for my JK. Who can I talk to about getting this done?
Totally. I can do wrench work all day, but electrical has me pulling my hair out.

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post #18 of 48 Old 04-19-2013, 12:10 AM
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You can order a complete, plug-and-play headlight harness from Susquehanna Motor Sports (http://www.rallylights.com/detail.aspx?ID=4887, choose H13 to H4 non DRL), but they are pricy at over $160.

You can order a Putco H4 wiring harness off Amazon for less than $30, (http://amzn.com/B001P29X4G), then cut-off the H4 Male plug and replace with an H13 Male plug using solderless (crimp) connectors. The plug is under $6 from Susqehanna (http://www.rallylights.com/detail.aspx?ID=1409).

However, I think that if you are going to be modding your rig and don't want to spend an arm and a leg on an sPod, learning basic electrical wiring is an important skill. I know lots of people who are afraid to do a little wiring but will happily cut and weld on their suspension and frame all day. This makes no sense to me.

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post #19 of 48 Old 10-23-2013, 09:29 AM
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Looks like I am another bringing it back from the dead poster! Is it possible to modify the harness to light the low beam by itself while allowing the low beams to stay on when switching to high beam?
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post #20 of 48 Old 10-23-2013, 10:01 AM
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My work around was triggering my headlight relay from the parking lights on the fenders . . . cant remember the last time I wanted JUST my parking lights on. Stay's on with high beams too.

The unlock/lock flash does NOT trigger this wire and (obv) neither does the turn signal.

>> I dont believe it is part of the Canbus system as well no no freaked out relays or codes (High beam wire freaks out my relay by turning it on and off 10000000 times a second lol, blew the bulbs :-/ )

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post #21 of 48 Old 10-23-2013, 10:35 AM
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Great idea. Thanks.
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post #22 of 48 Old 11-07-2013, 08:52 AM
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Where is the Jeep side connector with yellow, blue, and black wires as indicated in the diagram? This will be the point of connection to the new relays, will it not? Where would I find this connector in the Jeep wiring harness?
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post #23 of 48 Old 05-12-2014, 01:49 AM
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Jeep Side Connector

Hi All...just came across this thread as I wanted to do my own harness as well. Where is the jeep side connector on the diagram located in the jeep, please?

Sorry if this is a stoopid question, but need to know..thanks
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post #24 of 48 Old 11-23-2014, 10:08 PM
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Thanks for the post and repliers. I just made mine for $60. I needed everything but the connectors and solder kit. I reused the stock H-13 connectors as I just added the Sylvania Ultra bulbs to the stock headlite housings. From reading so many posts about this mod, higher watt bulbs, Cibies, Hellas, HIDs, LEDs etc. with so many different experiences by so many people, I figured I would try what is cheapest first. All in $100. Just testing in the garage is showing a big improvement as the whole garage was lit up!
Saying all that, if you're contemplating this mod, be prepared for a lot of work building a harness. Start to finish and install was 5 straight hours of work. I would buy a harness from a vendor if time or this kind of work isn't for you as they're only about $120.
I've done headlite "direct power from the battery" mods in the past, so I kinda knew what I was getting into, but this was the first CANBUS one.
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post #25 of 48 Old 01-23-2015, 05:45 AM
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So I did something different and bought a H4 Relay Harness off of eBay that came over on the boat. Surprisingly it's good quality but I suffered the same issue where my relay started buzzing and the readings of my voltage were everywhere. So I think I am going to get a capacitor and see if that fixes it. My H4 lights work great without the harness but I would like to supply the full 12 volts to them. So the 220pF capacitor would give me quick response going from low/hi/low etc...?

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