Alternator wire thickness

[J-440]

Evening all. I have a 140amp, GM style, 1 wire alternator from Powermaster. It's putting out 12.2 volts at the alternator terminal. The battery is losing volts when the engine is running and when the positive terminal on the battery is taken off, the engine dies. This alternator is new but has been sitting for 9 years. Bad internal regulator? I am also using 8 gauge wire from the alt to the battery. Powermaster calls for 6 gauge wire. This still does not explain the volts coming from the alternator terminal though. Any thoughts?

[astroracer]

Take a look at this article from Mad Electrical about 1 wire alternators:
http://madelectrical.com/electricaltech/onewire-threewire.shtml
It's very possible the alternator is not getting a good voltage sensing signal and simply doesn't go into "charge" mode...
As far as wire size goes I would look through the Mad site and do some reading. I am running 4 ga cables for all of my charge and ground cables to and from the battery and alternator. It is much safer to go too big then too small....
https://static1.pt-content.com/images/pt/2013/10/MVC057Fvi-1.jpg
https://static1.pt-content.com/images/pt/2013/09/MVC022Fvi-1.jpg
Mark

[vette427-sbc]

Just a note on Marks picture... It looks like youre using similar wire to something you might wire an audio amplifier with. Not saying that you are using the bad wire, but lots of those kits are far from the gauge they say they are, and lots of them are Copper Clad Aluminum which is not nearly as good as a 100% copper automotive wire. The insulation is also not rated for underhood temps like automotive specific wire. I had a customer that had a trunk mounted battery and was using a cheap 1AWG audio cable as his main power feed. The starter would barely be able to turn the car over because of such a big voltage drop from the wire. Ended up trashing that wire for a proper 1AWG automotive spec wire which fixed the problem.
Not raggin' on you Mark, just making sure people are aware of the low quality stuff out there that will cause issues. Real copper isnt cheap!

[astroracer]

Just a note on Marks picture... It looks like youre using similar wire to something you might wire an audio amplifier with. Not saying that you are using the bad wire, but lots of those kits are far from the gauge they say they are, and lots of them are Copper Clad Aluminum which is not nearly as good as a 100% copper automotive wire. The insulation is also not rated for underhood temps like automotive specific wire. I had a customer that had a trunk mounted battery and was using a cheap 1AWG audio cable as his main power feed. The starter would barely be able to turn the car over because of such a big voltage drop from the wire. Ended up trashing that wire for a proper 1AWG automotive spec wire which fixed the problem.
Not raggin' on you Mark, just making sure people are aware of the low quality stuff out there that will cause issues. Real copper isnt cheap!

Thanks for lookin' out for me Chris! You are right about the audio part but this is high quality copper wire (it was not cheap...). 720 strand or something like that, so it is very flexible. I am also running 1/0 cable for the starter and battery hook-ups. There is a difference between 1awg "wire" and 1/0 cable so I am not surprised it was a little light.
Here is a pic from my build thread. This is the 1/0 cable routed to the starter solenoid. Most of these runs are very short. The longest is the run up to the starter motor which will be about 13 ft. so the 1/0 will do the job very well.
https://static1.pt-content.com/images/pt/2013/10/MVC045Fvi-2.jpg
This cable will only be hot during start. All of my charging and power distribution will be thru the block I show in the previous post.
Mark

[J-440]

Mark, I also see that you have a ground for your alternator. Mine does not have one (although I could easily install it). I thought that the alternator itself was the ground? Also, there is a rubber boot for a harness of some type? It's a 140amp, but do I need a harness (cost me $9). It's got 3 wires: a thick red and a smaller black and brown. Do I need to install it and if so, where do the wires go? Thanks again.

[astroracer]

Depends on how your "1-wire" alternator plugs in. If it has the connections to hook it up as a three wire you would be better off to hook it up that way. If it doesn't, I don't know what to tell you. The 1 wires just don't do the job as well as a three wire. It takes a certain amount of rpm to get the alternator working and. if you are doing all of your voltage tests at an idle it probably isn't in charge mode.
As far as grounds go, they are as important as the hot leads, if not more so. You see a ground on the alternator, yes, and the engine block will also be grounded to the same stud on the frame as the alternator and a bunch of other components. Relying on bolted interfaces to ground components is not a good method. Paint, chrome and rust have very good insulating properties. I always ground my components individually and usually go with a big wire to do it.
Mark

[J-440]

Mark, this is what Powermaster told me. Run a 13' (4 gauge) wire from the alt to the battery in the trunk. Then run a 4 gauge ground wire from alt to chassis. Omit the 3 wire harness and I'm done. That sound right to you?

[astroracer]

Mark, this is what Powermaster told me. Run a 13' (4 gauge) wire from the alt to the battery in the trunk. Then run a 4 gauge ground wire from alt to chassis. Omit the 3 wire harness and I'm done. That sound right to you?

Those are 4awg's you see in my pics. If you run the charge lead to the back I want you to put in at least a 200amp fuse (in the back, near the battery) just to protect that lead in case of a short.
We really need to know how the rest of your system is wired. I highly recommend switching the alternator back to a three wire. That is the only way you are going to gaurantee the alternator knows what output your charging and accessories systems need.
Here is a quote from the MAD site:
"The ONE-WIRE, without REMOTE VOLTAGE-SENSING option, as an “intended up-grade” from a 55Amp externally regulated to a 100Amp ONE-WIRE can result with dim lights, weak ignition, and weak performance in general. (Especially so when a factory-original” type wire harness system is used.) And at M.A.D. we have received many phone calls from people who have experienced the result of such conversions."
If you do this AND upgrade your wire size and quality I think your charge issues will be eliminated.
Mark

[astroracer]

Also! Make sure your ground connections are clean of paint and rust. Where is the battery grounded in the back? Body or frame? Make sure the grounds have a clean path to follow. If you are grounding the alternator, engine, and body to the chassis in front, ground the battery and body to the same side of the chassis in the rear. Use those star washers under all of your ground connections to improve bite.

[J-440]

Ok, I've got an electric fan, electric water pump, power windows, EFI, Halo headlights, and soon to be mild stereo running on a single wire 140amp alt. Battery in trunk with the negative post ground to the frame with a good clean ground. Motor is grounded to frame and body is grounded to frame. At first my alternator had an 8 gauge wire going straight to the battery and no ground wire (thought the alt grounded itself). I've got some 4 gauge wire coming along with a 4 gauge ground strap. I've also got the small harness to convert back to a 3 wire setup if need be. Just need to know where those extra wires go to if I hook it back up. There's a thick red and a small black and small brown wire.

[vette427-sbc]

Thanks for lookin' out for me Chris! You are right about the audio part but this is high quality copper wire (it was not cheap...). 720 strand or something like that, so it is very flexible. I am also running 1/0 cable for the starter and battery hook-ups. There is a difference between 1awg "wire" and 1/0 cable so I am not surprised it was a little light.
Here is a pic from my build thread. This is the 1/0 cable routed to the starter solenoid. Most of these runs are very short. The longest is the run up to the starter motor which will be about 13 ft. so the 1/0 will do the job very well.
[img]http://images18.fotki.com/v60/photos/5/904975/12480003/MVC045F-vi.jpg[/img
This cable will only be hot during start. All of my charging and power distribution will be thru the block I show in the previous post.
Mark

I figured you knew what you were doing, judging by the rest of the build... Theres alot of people that think wire is wire.

semi thread-jack over :usa:

[TheJDMan]

First off, you mentioned a 12.2 volt reading. That indicates the alternator is not working and you are just reading the battery voltage which also accounts for the engine dying when you disconnect the battery. You should be seeing 13.5 to 14.5 volts with the alternator charging correctly.

I also agree with Mark on using a sensing alt. I purchased a 140amp Powermaster 1 wire 12SI based alternator. I was not happy with the way it charged so I replaced the regulator with a standard AC Delco regulator and converted it to a three wire setup. Much better charging system performance.

[astroracer]

Ok, I've got an electric fan, electric water pump, power windows, EFI, Halo headlights, and soon to be mild stereo running on a single wire 140amp alt. Battery in trunk with the negative post ground to the frame with a good clean ground. Motor is grounded to frame and body is grounded to frame. At first my alternator had an 8 gauge wire going straight to the battery and no ground wire (thought the alt grounded itself). I've got some 4 gauge wire coming along with a 4 gauge ground strap. I've also got the small harness to convert back to a 3 wire setup if need be. Just need to know where those extra wires go to if I hook it back up. There's a thick red and a small black and small brown wire.

You need to verify your alternator is 3-wire ready. if it can't be retroed back to the 3 wire you will need to upgrade or replace it.
Here is a pic I use as reference:
https://static1.pt-content.com/images/pt/2013/10/10SIc2-1.jpg
Are you using the stock harness? The sensing wire should be tied into the main power distribution junction in your harness. The others are explained in the pic. On my stock van harness the sensing wire bolted to a stud on the front of the fuse box in the engine compartment. I will be wiring my alternator using the stock hook ups and up-gauged wire.

[bovey]

Very timely thread. I just had an issue last night with my alt. When out this morning and found this.

This is a 4 gage wire from my alt to my battery (14" long) - this WAS charging cable to my battery. No wonder I had a dead battery.
84150

So I cut open the AUDIO wire I had used. Roughly the first 4 inches was hard as a rock, the rest of the wire was fine.
84151

Pulled it out - for curiosity.
84152

When I found fresh wire this powder came out - the smell burnt the inside of my nose.
84153

About 6 inches inside the wire was corroded to death.
84154

Finding better wire tomorrow. As you say - not all wire is created equal - I know this and I still got caught.
Feel free to learn from my mistakes.

[83tb]

what kinda wire was that burned up like that? You have a short somewhere?

[bovey]

First. The wire. I was in a pinch and had to buy a chunk of Pyramid High Power Pro Wire... (sigh)... and forgot about it.

2nd. I did have a dead short in the interior that took out a wire that excites the internal regulator, the lens had came loose from the LED indicator light and expose the leads (joy). No other wire was hurt under the hood. This was very corroded and the dead short happened last week. Based on how I have it wired, I think it's co-incidence as wire that connects the charge circuit and the excite circuit was untouched.

Fortunately, it's an easy fix. And I was lucky that I shut down right at my garage door. Normally, not that fortunate.

[J-440]

Ok Mark, thanks for the diagram. I'm not using any of my stock harness. Bought some 4 gauge wire and a thick ass ground strap. Gonna save about 12' of wire and use just enough from the alternator to the starter relay.