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  #1  
Old 08-31-2011, 08:48 PM
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Alternator ??

I purchased my Alt. I thought I wanted a 1 wire setup but I was able to find a stock harness in good shape. So this new one had a regulator wired to the back of it.
Just take it off and use the fenderwell mounted regulator right? Sounds good.

So now it's been a while and my battery is defenitely not up to snuff. I start digging and fine that someone cut off the stator wire. Not only at the Alt but also in the harness itself.
So obviously I'm missing the stator wire but would the fact that the engine has only been run at low rpm's just in and out of the barn add to the problem?

Thought I read somewhere that alternators had to reach a certain rpm to provide recharging power.

I'm thinking the Alt should be fine as it was originally externally regulated and not wired any different inside.

Also my gage does not appear to be operational. Just stays the same all the time.

Whatcha think?
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Old 08-31-2011, 09:52 PM
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I can't tell you if an internally regulated alternator with the regulator removed will act the exact same as an externally regulated alternator, and no one else should be able to, either. Theoretically, yes, it makes sense, and from a high level it seems like it should work, but earlier-model alternators are designed with the expectation that the regulator will be placed several inches away at a slightly different ground potential; while modern alternators are designed under the assumption that the regulator is directly connected on the back. Does it make a difference? I don't know.

If you have an ammeter on the dash, then the S or STA (stator) post of the alternator should only go to the electric choke, and nothing else. The S post of the voltage regulator, however, MUST have a keyed power source. If this is not the case, the alternator will never come online.

There is no "minimum RPM" for alternators to work. Alternator output is a function of RPM; this is because of Faraday's law (the faster a magnetic field changes, the larger the voltage induced through a loop). The faster the engine turns, the more current the alternator can produce. Alternator output is simply lowest at idle, but even the lowest-rated alternators are designed to be capable of sufficiently charging the battery in a stock setup. The regulator's job is to keep the alternator output fairly constant as RPMs go up and down, and the load changes. Obviously at lower RPM, the regulator demands more of the alternator.

The non-op ammeter is fairly common; don't expect much from it. An aftermarket voltmeter is a much more effective diagnostic tool. The voltage is what the voltage regulator regulates, so it's much more useful to see what that actual number is.
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Old 08-31-2011, 10:03 PM
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When I had used a GM 1 wire alt on my ford I had to hit 2000 rpm's to excite the alt to charge . I can't remember the way I wired it been along time ago, cause I did a 3G conversion .
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Old 08-31-2011, 10:10 PM
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When I had used a GM 1 wire alt on my ford I had to hit 2000 rpm's to excite the alt to charge . I can't remember the way I wired it been along time ago, cause I did a 3G conversion .
If your alternator would not charge below 2000 RPM, then something is wrong. Otherwise your battery would drain at idle.

Folks, it only takes two things for an alternator to charge: (1) Field current by applying voltage to the F terminal, and (2) actual rotation of the alternator. The output just has to be big enough to handle a standard load at low RPM. Obviously the voltage increases as RPMs increase; and this is when the regulator backs off on the field current. At lower RPMs, field current is at a maximum, to maximize alternator output in the wake of reduced RPM.

If your battery voltage stays between 13 and 14 volts at idle, then your alternator is charging. This means the available alternator output is at least as great as the current drawn by the ignition system and whatever other loads you have engaged (like headlights, etc).
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Old 08-31-2011, 10:27 PM
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That is why I stop using gm alts cause everyone I got from the parts house had one of those neat little cards in the box stating that the alt had to hit 2000 rpms to start charging . There was nothing wrong with the way I installed them . But the gm alt also had problems keeping up with the electrical demands
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Old 08-31-2011, 11:03 PM
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X2 the GM 1-wire alternators need to hit the high idle to "excite" the charging process then they usually do just fine at low idle.

My Kawasaki motorcycle seems to be the same way.

Josh
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Old 08-31-2011, 11:11 PM
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X2 the GM 1-wire alternators need to hit the high idle to "excite" the charging process then they usually do just fine at low idle.
That would make sense then - that means it self-excites at 2000 RPM, then it's online. Hence the need for only one wire.
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Old 08-31-2011, 11:19 PM
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joshjones.thewelder
From what I have observed the Ford 3G doesn't "enjoy" a very low idle, think 550 rpm or less. There have been a couple members here that have installed a 3G and then complain about the alternator not charging at idle and come to find out they have their 300-6 or 302 idling at 500 rpm. Bump it to 600 or more and it is fine.

Makes sense to me, it seems every modern engine is designed to idle at around 700-800 rpm...

Both my diesels, my 2.9 Ranger and every Nissan I have owned (1997 Pathfinder, 2003 Supercharged Frontier and my current 2004 Maxima) all idle 700-750.

Josh
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Old 09-01-2011, 06:34 AM
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I don't remember the S terminal going to the choke in my Haines manual. I'll double check. I don't even have the elec choke anymore.

Thanks for the help guys.
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Old 09-01-2011, 08:26 AM
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I don't remember the S terminal going to the choke in my Haines manual. I'll double check. I don't even have the elec choke anymore.
If you're not using an electric choke, and you have the ammeter setup (as opposed to an ALT light), then the S/STA terminal of your alternator doesn't need to go to anything.

The S terminal of the regulator, however, requires a keyed power source.
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Old 09-01-2011, 09:19 PM
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Looking at view of a 74 it is a white wire with black stripe going from Alt to regulator ( S terminal) which has a 3 prong connector. Just need to make sure it is hot with key on and I'm good to go.....I hope.

Thanks for the input everyone.
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Old 09-01-2011, 09:35 PM
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The version you're describing, which has a wire from the S post of the alternator to the S terminal of the regulator, is for an ALT light setup. These are wired differently. In this setup, the keyed power source goes to the I terminal. The S terminal acts as a "ready" signal from the alternator to shut the ALT light off once the alternator starts to charge.

If you have an ammeter, there is no connectivity between the alternator and the S terminal of the regulator. The S terminal of the regulator simply gets a keyed power source. Nothing goes to the I terminal.
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Old 09-01-2011, 10:14 PM
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This should help. I have the gage, not the light.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

I'm not 100% but I'm almost positive this was the stock setup. 1973 Camper Special.

4 wires going to the Alt.
Large black is batt.
Cut white wire I believe went to stator.
Small black is ground.
Orange is field.
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Old 09-01-2011, 10:14 PM
 
 
 
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