Advice for a Headlight wiring harness?

I've been reading GoJeep's instructions for a 10-gauge headlight wiring harness, and I'm going to make one. I've also searched this forum and read the other posts on it.

But before I start my own, I just wanted to get another thread started on it to see if anyone has any specific advice for making it. If you were going to do it over again, what would you do differently? Or if you've never made one, what possible problems can you forsee?

Thanks!!

I put the relays and fuzes up by the firewall (next to my RENIX "football" tank) for easier access - which still ends up with the power going through about half the wiring it did stock.

I'm inclined to redesign that to put the relay/fuze box next to the battery - but I'm also bent on redesigning all the underhood wiring anyhow, so I'll give that a seeing-to when I do it all...

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GoJeep did his next to the battery and fuse box ... looks like it turned out great. I'm going to try to design some little cover to put over the relays so that they are somewhat protected. I also like that style of in-line fuse that he uses on each circuit.

If you look, you should be able to find a relay box instead - I got mine for about $30 from Susquehanna Motorsports (Hella-made, splashproof, and has mounting feet to bolt it down.) I also used a fuze block - just to keep things organised.

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good advice ... do you have any pics? Sounds like you did a great job.

Also ... did you run a wire from your OEM headlight plugs up to the relays, or did you wire the OEM power source directly into the relays? It seems kind of inefficient to me to run the OEM wires all the way to the front of the vehicle, then run another wire back up to the relays. But then again, I'm hesitant to cut that heavily into the stock harness.

I run NO extra power or headlamp power through the OEMR harness - the power is provided through a separate circuit that I wired up from scratch. I only use the OEMR wiring for "triggering" the relays - which means that I've gone from about 5 amps a light to a total of 1/4-amp, I think. The mains power is provided seaparately, through an 8 gage wire off of a distribution post.

Therefore, when I turn on my lights, power goes through the switch, forward to the OEM plugs, and thence into the relay coils - and to ground. Then, a separate circuit provides power to the relay contacts, which then goes through the headlamp filaments, and thence to ground.

After all, what's the point in providing a relay to shorten the power path, if the obstruction is still present? That's the idea behind pulling another power circuit. If I had pix, I'd post them for you - but I haven't any.

Once you've got the wiring done, you can run it anywhere that is convenient - and away from heat and moving parts. I also used convolute tubing to prevent insulation chafing near cut edges (while the insulation on the wiring I used is both double and heavy - I take no chances.)

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5-90 said:

I run NO extra power or headlamp power through the OEMR harness - the power is provided through a separate circuit that I wired up from scratch. I only use the OEMR wiring for "triggering" the relays - which means that I've gone from about 5 amps a light to a total of 1/4-amp, I think. The mains power is provided seaparately, through an 8 gage wire off of a distribution post.

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Yes ... I understand that completely. I misspoke when I said "OEM power wire." I should have said the "OEM former power wire now used as the trigger wire (Hooked up to the 86 post on the relay)" The real power on my system will come from the battery to the 30 post on the relay, then out the 87 post to the headlights themselves.

So ... what I was wondering ... why run the OEM wire all the way down to the OEM headlight socket, and then run another wire from there up to trigger the relay switch, when you can just cut the OEM wire and feed it directly into the trigger (86) post on the relay. The only thing holding me back from that direct route is a hesitation to cut into my harness that heavily.

I used the Hella fused relays, they have a spade fuse built into the side of the fuse, did put dielectric grease on the legs to keep corrision to a minimum. As for relays always mount them feet down, otherwise you will get condensation collecting in the can that covers the relay and it will short out the contacts.
I also put mine between the battery and power distribution center. Attached with self tapping screws to existing holes already there. Will probably make a bracket to hold more as I add more lights..

RichP said:

I used the Hella fused relays, they have a spade fuse built into the side of the fuse, did put dielectric grease on the legs to keep corrision to a minimum. As for relays always mount them feet down, otherwise you will get condensation collecting in the can that covers the relay and it will short out the contacts.
I also put mine between the battery and power distribution center. Attached with self tapping screws to existing holes already there. Will probably make a bracket to hold more as I add more lights..

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Good advice about the feet down and the dielectric grease. Thanks.

5-90 said:

I put the relays and fuzes up by the firewall (next to my RENIX "football" tank) for easier access - which still ends up with the power going through about half the wiring it did stock.

I'm inclined to redesign that to put the relay/fuze box next to the battery - but I'm also bent on redesigning all the underhood wiring anyhow, so I'll give that a seeing-to when I do it all...

5-90

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I'll be sure to keep you informed on my retrofitting of a 94 PDC into my 87 Renix. SHould work out well. I'll be using about 1/3 of the capacity, so I'm planning on using it for a headlight harness and a few other things. I've got all the different colors metered out, and just need to match them up o the renix fusible links. I'll probably get to it next month, when it get's a bit warmer out. I find it hard to work on wiring with gloves on.

Thanks for all the advice.

Here are some links to all the info that I have found, which might be helpful to others planning this upgrade:

GoJeep's instructions:
http://go.jeep-xj.info/HowtoHeadlightLoom.htm

Wiring diagram from rallylights.com:
http://www.rallylights.com/useful_info/headlamp_wiring.htm

PartsExpress information on use of relays:
http://www.partsexpress.com/resources/relays.html

PartsExpress .pdf file with even more info:
http://www.partsexpress.com/pdf/500-001.pdf

Hope this helps. Good luck to everyone.

87manche said:

5-90
I'll be sure to keep you informed on my retrofitting of a 94 PDC into my 87 Renix. SHould work out well. I'll be using about 1/3 of the capacity, so I'm planning on using it for a headlight harness and a few other things. I've got all the different colors metered out, and just need to match them up o the renix fusible links. I'll probably get to it next month, when it get's a bit warmer out. I find it hard to work on wiring with gloves on.

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Cool - I'll look forward to it. A writeup with pics would be greatly appreciated - no need to hurry, tho.

One thing I'm working on - I'd like to find a source for "blowout currents" for fusible link wire in various gages, so I can replace the fusible links with fuzes instead. No need for the PDC, but I'd like to re-engineer all the wiring underhood one of these days.

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