Headlight relay questions

[NedFlanders]

Getting ready to do the relay mod for my headlights and was wondering what size wire most of you use? Looking at the stock wire (16 gauge), and considering how far it runs before finally getting to headlights, would there be any noticeable benefit in using 12 gauge wire? Or would it work just as well with 16 gauge since I wont be running any aftermarket lights, just the stock halogens.

 

[firebane]

LOL. When I plan to do this I am going to be redoing it from the bulkhead connector out with all new 14g wire. Is it necessary? Probably not but I like to do things crazy.

 

[83kid]

Did mine with either 10 guage or 12 gauge, pretty sure it was 12, and it does it more than well enough

 

[rich weyand]

If you are putting in a relay kit, the longest wire run is probably 6 feet. Loss isn't an issue.

BTW, I got my relay kit here for single headlights. For $25, I don't think I could have built it up myself for that. Completely plug-and-play, with no wiring changes to the truck or the relay kit. It uses the existing truck wiring to run the relays. I didn't like their headlights, but the relay kit is top notch. Been on there three years, no issues. I got the "H4 9003 P43t". Search it on this page, it is about 20% of the way down this (long) page.

http://www.autolumination.com/headlights.htm

 

[NedFlanders]

If you are putting in a relay kit, the longest wire run is probably 6 feet. Loss isn't an issue.

BTW, I got my relay kit here for single headlights. For $25, I don't think I could have built it up myself for that. Completely plug-and-play, with no wiring changes to the truck or the relay kit. It uses the existing truck wiring to run the relays. I didn't like their headlights, but the relay kit is top notch. Been on there three years, no issues. I got the "H4 9003 P43t". Search it on this page, it is about 20% of the way down this (long) page.

http://www.autolumination.com/headlights.htm

Yea but they use crappy relays, like the LMC kit. For something as important as headlights I dont want to cheap out and end up blind in a curve at 60mph.

I have some extra Bosch relays that I plan to use, just trying to figure out if there is any advantage to using 12 gauge over 16 gauge for a run of less that 6' like you said.

 

[rich weyand]

Yea but they use crappy relays, like the LMC kit. For something as important as headlights I dont want to cheap out and end up blind in a curve at 60mph.

I have some extra Bosch relays that I plan to use, just trying to figure out if there is any advantage to using 12 gauge over 16 gauge for a run of less that 6' like you said.

Well, I haven't had any problems in three years. I also have fogs in the bumper. though, so I do have other lights if need be.

16 AWG, for 6 feet, carrying 5 amps (65W bulbs) = .25 V of loss.
12 AWG, for 6 feet, carrying 5 amps = .1 V of loss.

 

[NedFlanders]

Well, I haven't had any problems in three years. I also have fogs in the bumper. though, so I do have other lights if need be.

16 AWG, for 6 feet, carrying 5 amps (65W bulbs) = .25 V of loss.
12 AWG, for 6 feet, carrying 5 amps = .1 V of loss.

Thanks, looks like no noticeable difference in light output.

Guess I will stick with 16 gauge, since its easier to work with.

 

[rich weyand]

Thanks, looks like no noticeable difference in light output.

Guess I will stick with 16 gauge, since its easier to work with.

It goes by the square, so it will be about 2% less light output with 16 AWG instead of 12 AWG. Bigger variance than that depending on where your voltage regulator locks in.

What I mean to say there is that the variance in lock-in voltage between different voltage regulators makes a bigger difference than that.

 

[NedFlanders]

It goes by the square, so it will be about 2% less light output with 16 AWG instead of 12 AWG. Bigger variance than that depending on where your voltage regulator locks in.

What I mean to say there is that the variance in lock-in voltage between different voltage regulators makes a bigger difference than that.

Is 2% noticeable? If im gonna do it I want to do it right. I have both 12 and 16 gauge on hand, the 12 is THHN so a little harder to work with over the 16 gauge automotive I have.

 

[rich weyand]

Is 2% noticeable? If im gonna do it I want to do it right. I have both 12 and 16 gauge on hand, the 12 is THHN so a little harder to work with over the 16 gauge automotive I have.

Not noticeable. The eye is logarithmic.

Get several different alternators out of a batch, and they will have lock-in voltages anywhere from 13.8 to 14.5 volts, a much wider range than the .15 volt difference with the two wire gauges.