Originally posted by afi292@Aug 13 2004, 12:26 PM
a harness will not make your lights too much brighter...
there are plenty of online calculators that you can use to see how many more amps a larger gauge wire will provide you. It has an input field for the length of wire too... and it will come out to be a fraction of an amp... your much better getting silverstars IMO. The wiring harnesses are mostly for if you are going to upgrade your bulb to a much higher wattage...
Jesse
A number of years ago I did an exhaustive test of light output of halogen bulbs. It turns out that once a voltage of 12-12.5v is reached, any additional voltage results in an almost exponential increase in light output. The best stock wiring harness I have run across is that in my 97 XJ6. The stock harness gave only 0.3v drop. The harness on my 95 SHO gave a 1.1v drop. I build my own harnesses and they give no more than 0.1v drop.
In testing 100w halogen H1 bulbs, I found that, with a wire length of only 3 feet between the bulb and the battery, 10 gauge wire had much less of a voltage drop that 14 gauge wire. Using 130w or 160w bulbs really make this drop visible. All the driving in lights on my rally car use 10 gauge wiring and I have more light output than every other rally car I have seen.
In most cars the current to the headlights is fed from the battery to a breaker or fuse, to the headlight switch, to the high/low beam switch, and finally to the headlights. It is through this circuitous path (pardon the pun) that voltage drop occurs. My 95 SHO had the headlights grounded to the body via a (much too small) 20 gauge wire. Harnesses replace this path with something much better.
The key to the harnesses is the quality of the relay, the gauge of the wire, the quality and assembly of connectors, and the quality of the fuse/circuit breaker.
For my headlight harnesses I use 12 gauge wire. This seems to be the best compromise of cost vs voltage drop vs the physical routing of the wire. I take the main power for the lights from the alternator rather than the battery. I ground the lights to one of the alternator mounting bolts as well as the battery. The purist in me knows that there is a small voltage drop between the battery and the alternator. I use automotive circuit breakers rather than fuses. I have yet to find a fuse assembly that gives less of a voltage drop than a circuit breaker. I use crimp connectors on the ends of the wires and, after crimping the connector properly, I solder the crimp part of the connector. This causes solder to fill little air gaps within the crimp and adds to the strength of the crimp. I use silver based solder. I use dielectric grease between the bottom of the crimp and the insulation of the wire. I cover the greased area with heat shrink tubing. As the years go by, this technique stops a corrosion buildup inside the crimp.
You may think I'm going overboard with this voltage drop thing, but it really does make a difference.