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Tungsten

Building a Headlight Relay Harness

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Briefing:

I was tired of the headlights under-performing and decided to do something about them. At first I thought the problem was in the bulbs so I used super bright PIAA bulbs but the difference was very marginal. When I measured how much voltage the sockets were receiving, I was not surprised. There was a marginal voltage drop in the bulb sockets which explains why the bulbs don't work as bright as they should. The reason for the sockets running low on voltage is that they go through the tiny switch in the stalk and are powered by thin gauge wire which is not ideal for 65/45 bulbs. According to some math, the minimum wire gauge that should be run to those light bulbs for the distance of about 20 feet is 14 gauge. The factory Nissan wiring would only work if the wiring was under 10 feet long but it is not! See: http://www.amplepower.com/primer/gauge/index.html The way to solve this problem is to relay the wiring directly to the battery. A relay in this situation will take small power from the connectors and connect the power from the battery to the headlights. After looking around at some relay harnesses, I was not happy with any of them. They were still thin gauge wires with crappy Chinese relays. Unable to find anything decent and something that fit at the same time I decided to build my own harness which will use factory Nissan relays.

 

Required items:

2x High Temp Ceramic Male 9004 Connectors

1x Generic Female 9004 Connector

1x 14 or lower AWG triple conductor loop of wire, about 20 feet

1x Inline Fuse Holder with 20-30 Amp fuse

2x Ring Terminals

8x Quick Female Terminal Connects

2x Blue Nissan Relays (or 1x Black Nissan Relay)

 

Also needed:

Soldering Gun

Heat Shrink Tubes

Wire Loom

Electrical Tape

Wire Cutters/Strippers

 

You can also get one of these "upgrade harnesses" to get the proper plugs:

 

L3-9004_9007.jpg

 

Here are some pictures of what I had:

 

293515_10150262301254075_612879074_7595146_1663663_n.jpg

 

297906_10150272386714075_612879074_7694179_9691_n.jpg

 

301259_10150272386844075_612879074_7694181_3031587_n.jpg

 

The harness is not yet complete but it should be soon and I will post before and after photos.

Edited by Tungsten

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It does make one hell of a difference both the 88 and the 94 have it done

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You can also use a fuse block, if you are going to be wiring in more accessories for a cleaner look. I picked on up that holds 6 fuses which should be more than enough for me for 15 dollars. I just don't like those fuse holders hanging off the battery, at least looks wise.

Edited by adamzan

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313298_10150273558354075_612879074_7705219_6843489_n.jpg

 

All done!

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Nice work!

It will make a hell of a difference in the brightness of your lighting! On my truck, I used a manufactured harness (I was too lazy to make one up!) and the difference is amazing!

 

Please post a wiring diagram, I'm sure others will want to make one up!

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Let me do the math:

 

2x High Temp Ceramic Male 9004 Connectors = $16

1x Generic Female 9004 Connector = $5

1x 14 or lower AWG triple conductor loop of wire, about 20 feet = $20

1x Inline Fuse Holder with 20-30 Amp fuse = $5

2x Ring Terminals = $2

8x Quick Female Terminal Connects = $5

2x Blue Nissan Relays (or 1x Black Nissan Relay) = $10

 

Total = ~$63 in parts

 

Assembly time = 5 hours

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I'm still waiting for comparison pics.

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I'm waiting for clear night time to show you some night time pictures. The difference is there, trust me on that. Also, my high beam switch is no longer lagging when I pull it. Those Nissan relays are amazing, they turn on instantly. Here are some photos of my installation:

 

307211_10150274909099075_612879074_7717600_268485_n.jpg

 

314730_10150274908914075_612879074_7717596_5792739_n.jpg

 

303200_10150274909139075_612879074_7717601_1901431_n.jpg

 

317450_10150274909154075_612879074_7717602_5749787_n.jpg

 

310682_10150274909229075_612879074_7717603_6065127_n.jpg

 

Raise your hand if you want a wiring diagram! :D

Edited by Tungsten

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Alright, time to fire up Visio and draw you n00bs up a wiring diagram. :tongue:

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Wiring diagram would be nice to check against. Did you get the relays at the junkyard? I guess the colours are standard on all Nissans?

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Yes, they are JY relays. The blue ones are the most common ones.

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Here is the wiring diagram:

 

303768_10150275886604075_612879074_7728648_2479839_n.jpg

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Here is a comparison of all the lights shot during daytime. You can see the improvement in high beam.

 

296971_10150296452669075_612879074_7883633_1629930489_n.jpg

  • Like 1

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I just finished mine! :D

 

I took before and after pics, and the after pics do look a little brighter. It's running stock bulbs. (Ignore the waders.)

 

Picture24.png

 

Edit: Note that the difference here could easily be due to a slightly different camera angle. Tungsten's got better data. :)

 

My install wasn't quite as tidy. I hung the relays from a mending strap bolted to the battery clamp, and connected the old headlight wiring with crimp connectors, because nobody around here's heard of a female 9004. The only real trouble I ran into was a poor connection in one headlight, which I solved by bending the pins around a little. Anyway, I'm looking forward to giving this a proper test. :) Thanks for the schematic, Tungsten, it was a great help. :aok:

Edited by Slartibartfast

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I'm surprised that it isn't. :shrug:

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I'm pretty sure there already is one in the Garage/How To. I'll look for it and see about merging or whatever.

 

B

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Picture24.png

 

 

just fyi, it's really hard to judge the difference in this type of a photo. because I can go out to my truck, and take two different pictures, and have the height be just a quarter inch lower, and the light will appear to be brighter. Which seems to be the case in your photos. From what I can tell anyway.

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just fyi, it's really hard to judge the difference in this type of a photo. because I can go out to my truck, and take two different pictures, and have the height be just a quarter inch lower, and the light will appear to be brighter. Which seems to be the case in your photos. From what I can tell anyway.

 

IIRC the camera was sitting on the same stack of tires for both shots, in an attempt to get around this. Then again, my camera does weird things trying to compensate for low light levels. :shrug:

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Yes, most cameras will compensate for that. Use manual mode only when taking comparison shots of lights. From what I can tell, there was a minor improvement in relaying the headlights. The best part is not that you will get slightly brighter lights but that your switch will last much longer and not burn out.

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The headlights are relayed on R50s. Would an upgraded (i.e. thicker wiring) headlight relay harness still be worth the cost and effort?

Edited by Towncivilian

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No, not at all. Get some KC, IPF, PIAA, WARN, etc lights and wire those up instead.

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So the adapter you made uses the pass side stock plug to feed to the relays to "trigger" the new relays which than sends power out to the new plugs right?

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