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  #1  
Old September 7th, 2006, 12:03 AM
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Alternator wire

I had someone work on my Hella lights last year and they made a mess of things under the hood. Before they got in there, all of the Hellas were run off the back of the alternator for thier power before the fuse, and then on to the relay. They installed a battery distribution block with 4 posts, I assume because they ran out of room on the back of the Alt. I was looking around in there today trying to take in all of their interesting work. Then, I decided to redo it myself so that it didn't look so ghetto.
The way it is now- One power wire comes off the Alt and over to the power distribution block. Then all of the Hellas connect on that block and then out to the fuse holders, which lead to the relays.
Also connected to the distribution block is the wire that leads back to the battery, to charge it when the engine is on. This is 8 guage wire. Is 8 guage big enough? I don't know what was there originally, but I wish it was left alone. Any help or pics would be GREATLY appreciated.
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  #2  
Old September 7th, 2006, 12:12 AM
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Old September 7th, 2006, 12:15 AM
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Okay...maybe too much info at once. Sorry.
Is it okay to go from the back of the alternator to the dist block and then on to the battery?
Is it okay to use 8 guage wire to do this?
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Old September 7th, 2006, 12:27 AM
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So, what I think you are saying is that you removed the wire that normally goes from the alternator to the battery (to charge the battery when the truck is running) and now, instead of charging the battery directly off the alternator, you are running that wire first to the distribution block and then back to the battery. And you are wondering if a 8 gauge wire is big enough.

No. At least not for me. 8 gauge typically is good for about 75 or 100 amps, assuming no voltage drop. With routing, you are probably talking about 12 feet or so. Plus the voltage drop at each connection which would probably be 4 (battery, alternator, two at distribution block). I don't know what alternator you are running--some are 90 amp, some are 110 or 130, mine is 200 amp. I want the most efficient run of electrical wiring as possible because I run amps, winch, lights, ect. so I want max charge/efficiency not to mention not overloading the wiring, melting the insulation, and possibly causing a fire. I would run at least 4 gauge if I were you, or a 2 gauge if I were me, which I am and do.

That is assuming that I even understand your question which I had to re-read 4 times and took it as a personal challenge after Buck did not figure it out since I have been drinking IPA's all evening and am bored. I think I got it right, though... ;-)
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Old September 7th, 2006, 12:40 AM
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You understand correct.
I think that I am missing the brown wire. Questions:

I want to put it back the way it should be, so what guage is the brown wire and which connector on the back of the alt does it connect?
Once it connects to the positive terminal, is there a ground that I need to hook up, or is it already grounded at the Alt?
How is the brown wire routed back to the battery?
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Old September 7th, 2006, 01:00 AM
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I am not sure if the 97 is the same as the 94, but my wire goes from the alternator, under the bulkhead but above the chassis and then into the battery box. Forget the brown wire--bigger, when it comes to power, is better since all it will do is transport the power more effectively with less voltage drop AND your brown wire is the minimum that the truck stock would use (and sized correctly for the alternator, but still the minimum). Run a 4 gauge. If you upgrade your alt, run a 2 gauge. Or run a 2 gauge anyways in hopes to get a bigger alternator someday ;-). I can't remember if there is a grounding strap or if the mounting bracket acts as the ground--I just can't recall. Might have to check that in the morning, but you want to have the power and ground wires the same gauge, both the minimum of the maximum capacity of the alternator.
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Old September 7th, 2006, 09:50 AM
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Okay thanks, I'll give that a try.
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Old September 7th, 2006, 06:38 PM
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Okay, I ran a 4 gauge wire from the back of the alt to the battery. My GPS is showing the voltage when the car is on fluctuating between 12.3 and 13.0 volts. It is plugged into the lighter.
Seems like it should be higher to me. Should it?

I left one wire coming from the back of the alternator running to the distribution block, where the lights are powered.
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Old September 7th, 2006, 11:51 PM
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With voltage drop, it sounds just fine. Keep in mind, your lighter is probably using 14 gauge or so wire. Don't worry about that. Or, better yet, worry about it, come to Colorado, and we will spend the afternoon drinking beer, working on trucks, and listening to music and then go wheeling. Seriously, what is worrying you?
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Old September 8th, 2006, 12:13 AM
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Well...okay. I guess if I leave now I could be there in three days. I swear, everytime I get to Basalt I don't want to leave. My wife wants to move there too. I can't even imagine how nice it would be to take the 90 up the back side of Ajax and crest the top where you can see the entire town. Man, I feel like I am there now. And that, my friend, takes all my worries away.

Just wanted to make sure that the Alt puts a good charge on the battery. I had two batteries installed until yesterday. I took one out because the guy who put it in made it look so sloppy in the battery box, that it drove me nuts to look at it. I am looking for something a little neater now. Maybe going to go with two optimas, or something similar. The batteries I have are pretty big, and it gets hot in there, so that worried me.

Maybe I am just paranoid and worried about getting stranded somewhere. You know what they say, paranoia will destroy ya.
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Old September 8th, 2006, 01:41 AM
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I think that I know what you mean. I have not said it before, but I think it often (and let this be our little secret), but my D90 represents freedom to me. I keep it running better than most things in my life. If worse came to worse, if my little world ever shattered, I would take my D90 and go on a road trip. FREEEEEEEEEEEDOMMMMMMMM!!!!!!!!! (ala braveheart....)
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  #12  
Old September 8th, 2006, 07:06 AM
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I don't beleive that a large wire is neccesary for the charge circuit as the stock wire is plenty for the rate of charge that your alternator is capable of. We have the same size wire on the 150 amp altenators that are charging 8-4d marine batterys that run 2 1000hp Cat diesels and a shitpile of electronics etc.

For the gems equipped D-90 ('97) if I recall correctly the alternator charge circuit does run to the fuse panel and then the battery, same as the Disco and P38.
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Old September 8th, 2006, 11:57 AM
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Matt,

I happen to agree with you on the rate charge of the alternator for typical loading won't exceed 100 amps, but when adding winches, aftermarket lights, ect., I was under the impression that the alternator was capable of supplying the amperage of which it is designed. An argument could be made that it's maximum amperage is only used in spike conditions of short duration, and under those conditions a smaller wire can be sufficient but if you are changing the wiring I see no reason not to size it to the correct size equal to maximum amp draw possible. I come from an electrical background and am used to sizing wire based on breaker or circuit size. For auto's, 8 gauge is rated at 100 amps. If you know your max draw is under that and always will be, fine. Otherwise, sizing the wire for the max amperage possible in that circuit is the right thing to do 10 out of 10 times. In your example, you might even be able to use 10 gauge, but that still does not make it the correct gauge. If you have a 150amp potential, then you size the wire for that potential--that way if you change other parts on your system the wire is not the weak link. We all have seen recalls on autos due to undersizing of wiring--when Saturn had to recall their first batch of cars for this, not all of them had problems, but under a few conditions of max loading, several had wire shorts leading to trouble. You size wire to the potential draw. Always. It is the right thing to do. You can limit the potential draw with a fuse or breaker and that is fine too, but they would be sized to the wire, not the circuit.
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Old September 9th, 2006, 11:59 AM
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So...., I ran the wire from the alt to the battery. Will there be any problems doing this?
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Old September 9th, 2006, 01:03 PM
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Nope. Shouldn't be. Just make sure that the routing is such a way that with body movement and what not there is no possibility of pinching the wire.
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Old September 10th, 2006, 07:42 AM
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I'm certainly not from an electrical background, but I try to go by the US Coast Guard spec (CFR Title 46 subchapter T under 50 volt) thinking that if it's good enough for the Coasties who tend to overkill everything then it should be good enough for the Rover.

Got me thinking about the wiring. I checked the boat which is #4 wire which alone in the engine bay is rated at 180amp.

Hmmmn......the 8 guage wire I've been useing (Ancor, tinned) is rated to 120amp. (4ft run, single, in the engine bay)

The Alt- fuse box- battery wire looks to be 6 guage which would seem to be plenty?

If you run the alternator wire directly to the battery you would eliminate the 100 amp fuse for the charging circuit, which I think is why the alternator wire runs through the fuse box?

Not trying to be a dickhead....this wireing shite is interesting to me and I allways need to know more.
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  #17  
Old September 10th, 2006, 10:18 AM
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You are not being a dickhead--not at all. You always post good information and I sure did not mean to make you feel that way--sorry if I did.

And, although I bypass the stock fuse, I agree it should still be fused—I have a fusable 200A link (I have yet to put it in), but I did not mention it and I totally should have. The stock wiring to/from my fuse box (8 gauge) just is not up to snuff. With the exception of my winch (and this wire), every accessory that I have is fused or circuit breakered and it will be eventually, too, when I figure out the right solution for it’s big draw—possibly a slow burn fuse that can handle the spikes of winching.

I suppose since I am currently putting a subpanel in my house and have “wire” on the brain, I was overzealous in my wiring discussion. I think it is worth stressing, though, that most car issues are electrical and most of those (IMHO) are do to aftermarket accessories tapping into existing circuits without proper consideration of the wire gauge being used. If people blow fuses, they just figure since they added stuff they will just put in a bigger fuse. I have seen 30A fuses on 16 gauge circuits because the owner kept blowing the smaller fuses. I think I will put my thoughts down in a future post on wiring in stead of belaboring the issue here as I think it is important.
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Old September 10th, 2006, 08:44 PM
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Thanks for all of this good info. If I was going to put a fuse in the line, what size would I need to use?
And, while I am at it, I am now thinking of fusing the winch as well. Any ideas on the size of the fuse for each of these, or any other way doing it?

Also, where is the stock alternator fuse located (under the hood, or behind the dash)?
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Old September 11th, 2006, 12:30 AM
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I was thinking of getting this:


http://www.monstercable.com/mpc/prod...&section=power

It looks like it can handle the power.
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  #20  
Old September 11th, 2006, 01:13 AM
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Style wise, that is the same one I have. Mine is a different "name" though they look identical. I am picking up a second one for my winch, if they still have any left.
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