Years ago on one of the Jeep forums, a guy did a test before and after the harness only on his Jeep.

He happened to have access to a lumen meter from work or something.

35% increase in output with only the harness on stock old bulbs.

Don't spend $29.95 for a harness. Shop local.

 

Yes, and yes.

I'm not clear on the details of what you plan, so I'll just offer some general advice (in no particular order):

Don't worry about the original wiring, or about any wire you add to extend it to the relay location (on the firewall?). Since that part of the circuit is only carrying the current that is needed to operate the relay, it just doesn't need much. Automotive relays typically only need about a quarter of an amp (~250 milliamps) to work, so if it's 18 gauge or better, you are fine. No need to go big here.

What you need to upgrade is the 12v supply to the relays, and the 12v from the relay to the headlight. You can figure out what size wire you need by first measuring the length of wires you need, and then using one of the many online wire size calculators to properly size the wire.

Use wire loom to protect your wiring and for a clean look.

Make sure you have a good ground for the headlights, and for your relays.

Use dielectric grease on all connections.

Use good quality connectors. Don't go cheap here. The best are the nylon type, preferably 3M brand. Don't go with the cheap vinyl connectors.


Use a good quality crimper. Don't use the cheap junk that comes in kits.

 

I want to install the headlight harness I purchased from jhc7399. Thing is that it is very cluttered by the battery with my cruise control so putting the relays somewhere over there will be a little challenging.

Also I might add lights to a brush guard I bought and put some on the rear.

Also I might wire in an ext idle switch but not a real one. Use one I am making with a relay.

https://www.cherokeeforum.com/f2/mak...switch-242355/

Also I am thinking about having an stock alt rebuilt by a guy in my area who does this stuff. He thinks he can get as much as 150 amps out of one.

Also going to up grade my battery cables to 2 or 4 gauge. They need to be replaced so I might as well upgrade.

I would also rewire the factory fogs that I put in my '00 that did not come with them.

https://www.cherokeeforum.com/f2/fac...e-them-220836/

So the plan is to add a aux fuse box, a circuit breaker, and put both them and all the relays on the firewall, by the brake booster, etc. Try to make everything all nice and tidy.

Leaning towards things like this:





Went to a place kinda local to me and started grabbing flag terminals for the headlight harness. Found 2 out of the 3 I think I need plus a crimper for flag terminals. Primary wire I can get from the store.

I am going to be using factory switches for the lights and fake ext idle.

Which brings up another question. Does there need to be a fuse in the wire for the 12V run source for the switches?

 

Yep. Much cleaner to do a bank of relays & fuses up on the firewall.



Good thinking, but don't get carried away with wire size. A lot of the kids do. It has more to do with "mine is bigger so I'm better!" than with actual benefits.

When I re-did mine I went 4 gauge. (Great quality, and I got them with the clear heat shrink on the ends so I can see if any corrosion ever starts.)

Look at it this way: The factory wiring is adequate. It's good enough. It has reliably started Jeeps billions of times. It works fine. 4 gauge is better than just good enough. More than 4 is a waste of copper.

IF you are going to run a winch, maybe run 2 gauge to the winch, but no need to go that big on your main wiring just because you are running a winch. It doesn't buy you anything. The winch power doesn't run on the main battery cables - it has its own. A lot of guys think they need huge battery cables because they are running a winch, but the winch wiring has nothing to do with the main battery wiring to the starter & vehicle.


One upgrade that is often overlooked is the battery to fenderwell ground. This is a weak point for Jeeps. I went to 6 gauge on that (overkill), and replaced the sheet metal screw with a 5/16" bolt, fed from the back side, and secured on the front with a nut over a washer, AFTER clearing away all the paint around the hole. Another washer goes on next, then the battery cable, then a washer and a nylon locking nut to hold it in place. All of that hardware is stainless steel.

And remember to upgrade the alternator to battery lead, if you are going to upgrade the alternator. Again, use an online wire size calculator to determine how big the wire needs to be. It should carry the full output of the alternator with less than 3% drop. I like to oversize one, and only one, wire gauge size over the calculated value.

Marine-grade wire is hard to beat. BestBoatWire.com makes some nice stuff at very good prices. You can specify your cable ends, colors, everything you need.

I also used . I like them better than the because they don't stick up, and they offer two places to connect cables, instead of just one.


Sounds like a very good plan.

Those are both top of the line. Excellent choice.



Not quite sure what you are asking. 12v to feed to the switch, then back to the relay? If so, yes, that needs to be fused. When in doubt, fuse it.

OTOH, when I use relays and switches, I prefer to switch the ground side of the relay, rather than the 12v.

Let's look at some relay basics: A relay is a switch (which carries high current), operated by an electromagnet (a coil, which carries low current). So there's a high current side, the switch, and a low current side, the coil.

To energize the coil, we need to apply 12v to one side, and ground the other. But it doesn't matter at all if we permanently connect one side to ground (the usual way) and switch 12v to the other side, or if we permanently connect one side to 12v and switch ground to the other side. As far as the coil is concerned, it's exactly the same.

We also need to bring 12v to the relay to the high current side to feed the (whatever accessory), right? So let's just use a small jumper to feed 12v from that terminal of the relay to the coil terminal. (We can use a piggyback connector for that.) Now, we run a smaller wire (18 gauge is usually just fine) to the switch, and the other side of the switch goes to a good ground point near the switch. No need to run 12v to the switch, and back out to the relay. No need for a fuse on that line, because it's just ground. Our switch still operates the relay exactly as planned, and we saved running 12v to the switch and back. We also saved one more place for a short circuit to do damage.

Now, if you are going to use lighted switches, that might take some finessing to work, but it can probably be done.

If not, get your switch 12v from inside the vehicle, rather than running it from your new fuse box, inside to the switch, and back. You only need about a quarter amp, so you aren't going to overload any interior circuits.


Always fuse as close as possible to the power source.

 

My guy was not sure of the exact outcome of what the amps will be on the alternator when he is done. Hopefully there will be a way to test to see. Figure if it comes in at 150 or less then 4 gauge. More then 2 gauge. Will most likely buy XJwonders cables.

No I was talking about the 12V run source for the switch. When I put factory fogs in my Jeep that did not come with them I used this diagram to wire them. So I used a fuse tap and picked an open terminal in the fuse box in the footwell that had power all the time. If I had wanted to could I just have run a wire with out a fuse to get the 12 volts? Reason I ask is that the aux fuse box link I put above has a 100 amp max. Now I know I need to run a fuse in the wire to the relays from the 12 volt source. In the case of my fog light install it was from the battery, like the diagram, and I used a 20 amp. So figure 4 accesories plus the headlight harnes puts me at needing 5 relays, well six cause the headlight harness has 2 but only needs on fuse, at 20 amps apiece puts me at the 100 max. Now if I need to run a fuse for the 12 volt run source to the switch I would have enough spaces for fuses but it would put me over the 100 amp max. Kinda making me think I would need a second aux fuse box.

Please forgive me. Out of all the things that I am not really good at electrical in the worst. I just want to try understand what I need to do to try and do a nice, safe, clean job. What the outcome, if this does happen, will be remains to be seen. LOL