Lighting Wiring Harness Upgrade
By Chris Henry, John Kua, & Josh Capps

An upgraded lighting wiring harness connects the battery straight to your headlights. The stock system is designed to do this but there is quite a bit of voltage drop by the time the current gets through the distribution center and through the puny high gauge stock wiring. This problem is further amplified during high current draw such as driving with your fog lights and headlights or using your high beams. There is a simple upgrade which upgrades all of the wiring to the headlights and provides a straight connection to the positive battery terminal. The harness is a somewhat generic harness designed to switch on both 9006 low beams and 9005 high beams. It is manufactured by Carshow and available through Kolak for less than $75. The harness is available for many makes and models (including ZJ's) but this install will me performed on a 2001 Grand Cherokee Limited. The first part of this article outlines the install and the second outlines the results.

The harness basically consist of two relays which connect straight to the battery, two connectors which plug into your stock headlight connectors (this tells the relays when to switch on and off), and four connectors which plug right into the back of your bulbs. All in all, there is no need to cut or splice a single wire, it is just a matter of plugging the connectors in. It sound like a five minute job but actually it takes an hour or so to do it right.

You can really start anywhere, but I started at the battery connection. I hooked up the power leads which already had rings on them. Some people have room to mount the relays in the fuse box as shown below. My 2001 WJ with fog lights did not have any room.

I simply stuffed the relays neatly into the dead space behind the passenger side headlamp assembly and frame. Connecting the passenger side is cake. Unscrew the bolt shown holding the headlamp assembly on and gently snap the headlamp assembly out with your hands, this may take some force because there are three snap connectors securing it.

With the headlamp assembly loose, just lay it facing down and unplug the factory connectors from the light bulbs and plug the factory connectors into the female connectors of the wiring harness, so when you turn the headlights on, the old wiring to the headlamps connects to your new wiring harness. The high and low beam connectors are notched differently so you really can't screw this up. Now plug the short pair of male connectors from the harness into the back of the low and high beam bulbs. Now, you must ground the two black connectors. There is a bolt handy to ground shown in the picture below cut the bolt is too big for the round connector on the ground, you can just clip the circle connector with wire cutters to make a spade connector or find another ground point. That is it, you're done that side, but don't put everything back in place yet. Here is the tricky part, getting the wires over the driver's side. A suggest buying some 1/2" wire loom available at Home Depot or you local auto parts store. This makes the install look factory and also adds some protection to the wiring.

Next, remove the driver's side headlamp assembly and lay it face down. Now put all of wires heading to the drivers side into the split loom and find a good route to the other side. I placed mine right under the front hood gasket as shown below. It makes it easier to lift the gasket out of place completely and route the wires using wire ties along the way to secure the loom.

Plus the connectors in on the driver's side and connect the two ground wires as you did on the passenger's side. Hop in your Jeep and make sure the lows and highs work. Now go over the install and make sure everything is secure and out of the way. Put the headlamp assemblies back in place and your done. You can use wire loom and/or electrical tape to tidy up the installation and make it look stock.

THE RESULTS

The table below include before and after voltage readings with engine idling.

	Before	After	Power Difference
Low Beams	12.57	13.13	9.11 %
High Beams	12.24	13.12	14.90 %

Power equals voltage squared divided by the resistance of the bulb. Because voltage is squared in the power formula a seemingly smaller difference in voltage at the bulb can equate to a significant power increase. As you can see, the power upgrade is significant especially with the high beams on. Now this difference is multiplied even greater if you decide to upgrade the wattage of the bulbs you are using.

It is an afforbable upgrade that positively will make your headlights brighter, the proof is in the voltmeter readings. Upgraded bulbs can also help the situation. The harness can handle bulbs up to 100 watts without any problem.

This kit is available at lighting specialty shops and from
kolak@aol.com