For what it is worth sharing my Hella relay harness upgrade. Thankful for all the information I found here before I under took the project.The results are pretty dramatic visually and statistically. As you can see from the attached photos The original OEM wiring utilizing the headlight switch for all the voltage resulted in at least 1.92v loss at the bulb. Running I had 13.8 at the battery and 11.9v at both bulbs. With the harness I pick up at least 1.5 volts and an overall loss of only 0.4 volts.

If light output is proportional to the 4th power of voltage across the filaments in the bulb, apparently an increase of lamp voltage from 11.9 to 13.4 adds another 400 lm. In real life terms they are much, much brighter. I can see the road and the high beams are ridiculously good. Running Hella H4 DOT with the regular 55/60 watt bulbs. In any event the change driving last night was so dramatic especially on HI-beams that it’s hard to believe this change makes such a fundamental difference.

I purchased hey Heller harness by Octane Lighting on Amazon for $36 prime. Dual High Low Beam Headlight Relay Wiring Harness H4/9003 With High Heat Ceramic Plugs




It’s a pretty good harness, better than the others I shopped with at least 14 gage wire. Utilizing my installation I added 3 feet high grade speaker wire to work the harness through the nose over to the passenger side headlight. Soldered all connections and added a chaffing guard. All changes are reversible - Except for the small hole I drilled to attach the relays on the passenger front fender well. All the best.





At the car running

Before:At the Headlights under load 1.92 loss

Hella harness

Ceramic plugs

lla Relays



Relay Mounting point

 

That's great! I purchased some random harness off of ebay and tapped into +12V at the alternator. Totally agree results are dramatic.

 

I clicked on your Amazon link and the harness that popped up was not a Hella harness, but one made in China with Chepai relays???? I was hoping for Hella as I "assume" it would be a better quality.

 

MSGGrunt

Your absolutely correct about the link. But the package I received (and received by others - see Amazon comments) is the Hella Harness in my pictures! Let us know what you get in your order. Out driving tonight. Remarkably how much better the lights are.

 

Order placed. I just hope I too get the Hella harness. I already have the conversion lights ready to go in.

 

Received the harness today and I am happy to report that it is a genuine Hella harness and not Chinese.

 

Sweet! Wait till you drive at night!

 

Does it make a difference if you tap into the alternator or the battery for the 12 Volt source? Now I am considering an upgraded bulb. The box say that the harness can support up to a 130W high/90W low bulb, but I am thinking this may be just a little overboard. I do need to be considerate of oncoming driver's and don't want to be that "A-Hole" blinding on-coming driver's and or being flashed constantly. Maybe 100/90 bulbs. Need to see if I can find a set of Narva or Osram bulbs as I have had good luck with them in the past.

 

I picked the battery for ease of installation and access and just ran down the RH side. . On the Jeep CJ forums they often use the alternator. They are another vehicle with a horrible OEM harness.

 

i made my own harness but take power from the alt.

as long as the bulbs are aimed right, a brighter bulb won't blind oncoming drivers any more than a 55w stocker.

 

Ordered 15APR, arrived today (17APR) from the Amazon link above. Received a Hella harness.

 

I had a 1.57 VDC drop through the stock headlight wiring setup.
Made my own harness with 12 GA wiring and picked up power/ground directly from the alternator.
Now have a 0.32 VDC drop through my relay harness.
Measurements taken between battery and the connector at the headlight (70/90W Hella bulbs).
Definitely a "true" upgrade.