Head light relay mod write up....WOW what a difference - Page 6 - JeepForum.com
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post #76 of 409 Old 09-11-2012, 03:22 AM
Hard_oNe
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Great writeup. My next to-do. First order the white face gauges.

Thanks for the reminder to buy the needle paint. Can you get any cheaper than $2.50? Bought it from HiPoParts.com


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1989 Jeep YJ - "go slow"
2007 Trailblazer SS (6.0 LS2) - "go fast"
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post #77 of 409 Old 09-11-2012, 04:57 AM Thread Starter
mudsweatNgearz
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Quote:
Originally Posted by Hard_oNe View Post
Great writeup. My next to-do. First order the white face gauges.

Thanks for the reminder to buy the needle paint. Can you get any cheaper than $2.50? Bought it from HiPoParts.com
$2.50 is pretty good.

I wondered why the baseball kept getting bigger and bigger....then it hit me!
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post #78 of 409 Old 09-11-2012, 04:59 AM Thread Starter
mudsweatNgearz
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Originally Posted by jeff_in_rc View Post
Thank you very much mudsweatNgearz, this is exactly what I was looking for.

Now on to a question, why the use of 10g wire? And why not use 14g wire?
Thanks everyone!
You could probably use 14 awg and get by. I recommend 10 or 12 awg to be safe.

I wondered why the baseball kept getting bigger and bigger....then it hit me!
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post #79 of 409 Old 09-11-2012, 09:18 AM
Que89YJ
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Here is a wiring refrence for current rating. Great refrence material.
The number where they cross is the max distance in feet you can run at that many amps.
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post #80 of 409 Old 09-11-2012, 09:31 AM
jeff_in_rc
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Very nice chart, now we need to know how many amps the lights really pull both low and high beams.
I don't know if my VOM will do that but I will see if we have a clamp on meter at work I can borrow.
Great info Que89YJ !!

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post #81 of 409 Old 09-11-2012, 09:51 AM
HurricaneRZA
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Originally Posted by jeff_in_rc View Post
Very nice chart, now we need to know how many amps the lights really pull both low and high beams.
I don't know if my VOM will do that but I will see if we have a clamp on meter at work I can borrow.
Great info Que89YJ !!
wouldn't it be the wattage of the lights divided by the voltage they run on?

So for one bulb,
55watt / 12v = ~4.58 amps

meaning two bulbs @ 55watts should be drawing ~9.16 amps from the battery/alternator ( I understand this is not counting voltage drop at the lights themselves and a buttload of other variables that alter the output).


Or did I just type nonsense and need to be quiet until I get my cup of coffee ?

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This is the most metal thing I have ever heard.
Quote:
Originally Posted by doublins View Post
I always get people coming over and saying things like "I wish I knew how to do that," etc- but they don't realize- at some point I didn't know how to do it either- I had to figure it out.
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post #82 of 409 Old 09-11-2012, 10:01 AM
jeff_in_rc
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Quote:
Originally Posted by HurricaneRZA View Post
wouldn't it be the wattage of the lights divided by the voltage they run on?

So for one bulb,
55watt / 12v = ~4.58 amps

meaning two bulbs @ 55watts should be drawing ~9.16 amps from the battery/alternator ( I understand this is not counting voltage drop at the lights themselves and a buttload of other variables that alter the output).


Or did I just type nonsense and need to be quiet until I get my cup of coffee ?
Nope, you made perfect sence and I thank you!

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post #83 of 409 Old 09-12-2012, 09:14 PM
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post #84 of 409 Old 09-12-2012, 09:26 PM
HurricaneRZA
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Quote:
Originally Posted by jeff_in_rc View Post
Nope, you made perfect sence and I thank you!
No problem!


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Tag
Like the thread tag? There weren't any, I added a couple though...

Quote:
Originally Posted by YoureverydayXJ View Post
This is the most metal thing I have ever heard.
Quote:
Originally Posted by doublins View Post
I always get people coming over and saying things like "I wish I knew how to do that," etc- but they don't realize- at some point I didn't know how to do it either- I had to figure it out.
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post #85 of 409 Old 09-12-2012, 09:41 PM
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Quote:
Originally Posted by HurricaneRZA View Post
wouldn't it be the wattage of the lights divided by the voltage they run on?

So for one bulb,
55watt / 12v = ~4.58 amps

meaning two bulbs @ 55watts should be drawing ~9.16 amps from the battery/alternator ( I understand this is not counting voltage drop at the lights themselves and a buttload of other variables that alter the output).


Or did I just type nonsense and need to be quiet until I get my cup of coffee ?
12 volts is an inaccurate number, considering the system generally runs around 13.6-13.8v with all of the lights on. Whenever doing load calculations for lights, I always use 13.6 volts as my baseline voltage.

So,

55w / 13.6v = 4.04a, or basically around 8 amps for both lights, if they are infact running at 13.6 volts. Basically meaning the current load will go down with this wiring upgrade.

All about that unibody life.
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post #86 of 409 Old 09-12-2012, 09:58 PM
HurricaneRZA
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Originally Posted by Xpress View Post
12 volts is an inaccurate number, considering the system generally runs around 13.6-13.8v with all of the lights on. Whenever doing load calculations for lights, I always use 13.6 volts as my baseline voltage.

So,

55w / 13.6v = 4.04a, or basically around 8 amps for both lights, if they are infact running at 13.6 volts. Basically meaning the current load will go down with this wiring upgrade.
Not an inaccurate number per se, but I see what you're getting at. Before I upgraded my grounds and alternator cables I hooked up the power the lights onto the side post of the battery because of the flickering, I get around 12-13v coming from the side posts so I just went for 12v since thats about where it stays most of the time. I didn't take into account lights running off of the top posts hooked up to the pos from the alternator and the post from the battery simultaneously

Quote:
Originally Posted by YoureverydayXJ View Post
This is the most metal thing I have ever heard.
Quote:
Originally Posted by doublins View Post
I always get people coming over and saying things like "I wish I knew how to do that," etc- but they don't realize- at some point I didn't know how to do it either- I had to figure it out.
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post #87 of 409 Old 09-12-2012, 10:41 PM
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Well like I said, you should always use 13.6V as your baseline number. Your battery will not charge if the alternator is pumping out anything less than about 12.6V, and they generally peak around 14.8-15V.

All about that unibody life.
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post #88 of 409 Old 09-12-2012, 10:50 PM
HurricaneRZA
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Quote:
Originally Posted by Xpress View Post
Well like I said, you should always use 13.6V as your baseline number. Your battery will not charge if the alternator is pumping out anything less than about 12.6V, and they generally peak around 14.8-15V.
I'll have to check the voltage output on the side posts of the battery tomorrow with the new voltmeter I got today (the other one told me I had 999v off the headlight then promptly died) while it's running, but it may still be in the 12v for anyone running lights on the side posts (be they head lights or auxiliary).
Honestly, I would be disappointed if they are at 12v at the side posts w/ motor running. It just means I have to move the lights back up to the top posts for slightly better output and leave the side posts for the amp and/or air compressor...

Quote:
Originally Posted by YoureverydayXJ View Post
This is the most metal thing I have ever heard.
Quote:
Originally Posted by doublins View Post
I always get people coming over and saying things like "I wish I knew how to do that," etc- but they don't realize- at some point I didn't know how to do it either- I had to figure it out.
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post #89 of 409 Old 09-13-2012, 06:14 AM
Que89YJ
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The voltage drop across the wiring from the harness is significant too. The whole point to the mod is to eliminate the loss from the switch contact and the wiring. The switch losses are by no means small. The reason the switches fail is because the resistance goes up significantly as the contacts wear and get dirty. When the resistance goes up the voltage drop goes up across the switch and causes it to fail. Stock would have a couple ohms resistance through the system. The relay makes a significant difference in reducing the losses from the resistance. 12 guage is good enough with the distance from the relay being only a few feet with the stock lights. The current draw is about 12 amps if I remember correctly for the low beams amd close to 20 amps for the high. It's been a long time since I measured it. The bottom line is eliminating that voltage drop.
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post #90 of 409 Old 09-13-2012, 08:11 AM
HurricaneRZA
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Quote:
Originally Posted by Que89YJ View Post
The voltage drop across the wiring from the harness is significant too. The whole point to the mod is to eliminate the loss from the switch contact and the wiring. The switch losses are by no means small. The reason the switches fail is because the resistance goes up significantly as the contacts wear and get dirty. When the resistance goes up the voltage drop goes up across the switch and causes it to fail. Stock would have a couple ohms resistance through the system. The relay makes a significant difference in reducing the losses from the resistance. 12 guage is good enough with the distance from the relay being only a few feet with the stock lights. The current draw is about 12 amps if I remember correctly for the low beams amd close to 20 amps for the high. It's been a long time since I measured it. The bottom line is eliminating that voltage drop.
Good to know, actual numbers are a lot more useful than theoretical numbers, thank you!

Quote:
Originally Posted by YoureverydayXJ View Post
This is the most metal thing I have ever heard.
Quote:
Originally Posted by doublins View Post
I always get people coming over and saying things like "I wish I knew how to do that," etc- but they don't realize- at some point I didn't know how to do it either- I had to figure it out.
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