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11-29-2005, 02:56 PM
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Hummer Guru
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I have the HUMMER factory light bar, with the stock 4 off road lights attached to it. I am planning on adding 2 more of the stock off road lights to the bar, to give me 6 in all. There is enough room, and they connect light to light, in a series.
My question is, will the stock wiring harness handle the load increase?
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11-29-2005, 02:56 PM
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Hummer Guru
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I have the HUMMER factory light bar, with the stock 4 off road lights attached to it. I am planning on adding 2 more of the stock off road lights to the bar, to give me 6 in all. There is enough room, and they connect light to light, in a series.
My question is, will the stock wiring harness handle the load increase?
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11-29-2005, 03:14 PM
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VTSTOMPER:
My question is, will the stock wiring harness handle the load increase? </div></BLOCKQUOTE>
You should be okay unless it melts. Then you're not okay.
Helpful, huh?
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11-29-2005, 03:15 PM
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Hummer Guru
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 "you smell that?"
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11-29-2005, 03:19 PM
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VTSTOMPER:
"you smell that?" </div></BLOCKQUOTE>
Too funny!
If nobody else has a good answer, I have a chart that shows how far you can run a given guage wire at different loads. If you know the wire size of the harness and the length of the run, it should be easy enough to figure out if it'll handle the load.
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11-29-2005, 03:49 PM
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If you know the wattage of all the lamps, then here's what to do. Sum the wattage, divide by ~10 to be conservative. This is the approximate amperage draw of all lamps (I have nto clue what the real formula with units is...I=PV or something like that...just that this is a rule of thumb).
Multiple this by 1.5 (150%) to arrive at a recommended peak amperage rating.
Then look at this wire sizing chart to find the best wire to accomodate your wattage needs.
For example, let's say you have 6 65W lamps. That's 390W. Divide by 10, multiple by 1.5 (or divide by 6 2/3). You get 58.5 amps. According to chart, you should use 10ga wire. You can probably get by with 12ga wire, but 10ga is safer.
I'm not sure what stock wattage and wiring sizes are, but if you find the existing wiring is too small a guage, then you probably shoould wire a new harness on a separate relay just to be safe.
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11-29-2005, 04:06 PM
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Nice chart find, ree! That beats the heck out of the MSWord thing I have.
The formula is, I believe, P = I x E.
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11-29-2005, 04:13 PM
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Hmmm, on second thought, I'm not sure that chart answers the question at hand. Again, I'm not sure but is RMS watts a good measure in this instance? Do RMS watts = lamp watts?
Or maybe that's a goofy question. I'll have another cup of coffee and have another look ... 
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11-29-2005, 04:20 PM
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Rodster, your're right about eh RMS watts. The 12volt.com is largely audio/security system buffs and most of the discussion seems to be with speaker systems.
But the gauge-amperage chart is good.
In my online research, I've seen umpteen references to the divide by 10 (or 12 depending on who you talk to) and add 50% for peak/spike demands at device startup as the "formula" for miscellaneous DC accessory wiring. This is pretty close to their RMS-amp table, but not exactly.
I take the approach, error on the side of the heavier gauge if you can bear the cost. It's safer.
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11-29-2005, 04:29 PM
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ree:
But the gauge-amperage chart is good.
</div></BLOCKQUOTE>
Distance is a factor, too, yes?
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I take the approach, error on the side of the heavier gauge if you can bear the cost. It's safer. </div></BLOCKQUOTE>
I hear that. I had a definite case of overkill going when I wired my roof lights.
Hopefully VT won't have to pull new wires to drive his extra two lights.
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11-29-2005, 04:50 PM
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by rodster:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ree:
But the gauge-amperage chart is good.
</div></BLOCKQUOTE>
Distance is a factor, too, yes?
</div></BLOCKQUOTE>
Yes. Distance is a factor. I think I've got a ref to a chart. Yes. Here it is.
Amps-Wire Gauge w/Distance for 12V DC circuit.
It's fine for circuits under 70A and only starts at 15ft. I think most circuits on an H2 are going to be under 25ft.
Unfortunately, I can't find a chart that starts at 1' and runs up to 25ft.
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I take the approach, error on the side of the heavier gauge if you can bear the cost. It's safer. </div></BLOCKQUOTE>
I hear that. I had a definite case of overkill going when I wired my roof lights.
Hopefully VT won't have to pull new wires to drive his extra two lights. </div></BLOCKQUOTE>
Yes. This just burns away the time for someone like me who knows just enough to decide to do it on his own, but not enough that he doesn't have to research it for hours before pulling the trigger.
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'03 pewter base H2
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11-29-2005, 07:20 PM
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I want to say the lamps are 55W...but I am not sure.
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11-29-2005, 07:23 PM
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yep
6 inch, 12 volt, 55-watt
Going from 4 to 6! I think that the distance is about 6+/- feet
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11-29-2005, 07:36 PM
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Any idea what size the wire(s) is/are?
And just 'cause I'm curious, where are you getting the 12v? Using a relay? Where's the switch?
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11-29-2005, 09:37 PM
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It is a stock factory GM wire harness for the offroad lamps. I am not sure the size of the wire...I will have to check it out.
What one is the most important? The power?
The wire comes from a connector *factory* under the dash, to the left and above the break pedal. I imagine it is getting all the power from some ACC pin in there.
The lamp switch is up by the map lights...factory mounting location.
I will get some pics for you if you would like...well - when the sun comes out again. 
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11-29-2005, 09:44 PM
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No need for pics. I was just curious.
The most important wires to know the size of are ones that make the long run from the interior to the roof.
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11-29-2005, 10:06 PM
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ok, I will check them out and let you know the size! thanks man!
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11-29-2005, 10:08 PM
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Better idea ...
PM your email address to me and I'll send the chart. I'd post it here but it's in MS Word. Your call.
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11-30-2005, 01:27 AM
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I bet your right Phil. If I remember right, the wiring is like a typical to a standard headlamp wiring that you would find under the hood, feeding one lamp each.
I might add a second switch and all like you said.
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