Can someone post a photo of the differences between a one wire and three wire alternator? I just saw what I thought was a three wire alternator in a magazine being called a one wire alternator. Which one has the two pronged pigtail coming off the body and a BATT stud on the back?
the difference is the regulator, the one wire has a self excited regulator otherwise they are the same.
Which one is pictured above? Three or one wire? I can't post what I saw in the magazine. I'm just wondering. The one in my garage is a 12SI, I guess, from the pulley on it...does that make it one or three wire?
Alot of rebuilders are taking all of the old cores they can get their hands on and converting them so even old looking alternators can be 1 wire.
Here is some really good tech that should clear up any questions: http://www.geocities.com/cantwait_forviolence/cj_alternator.html
That's a three wire. Most all one wire alternators require a certain RPM before they turn on and some will turn off if they go under that RPM. And from my experience more than half of the ones I dealt with would not shut off properly and would create a battery drain. I personally like the standard three wire set up with an "ALT" light instead of the inline diode. You know right away if your alternator stops working and as an added bonus on those style alternators, you can tell if it is undercharging, under rated for the application or just about to give up when the light starts to glow.
I like the 3 wire SI alternators too, find them easy to wire, dirt cheap out of the wreckers, and the ALT warning light is a lot nicer that not starting because you didnt realize it had quit. My understanding is that 1 wire alternators are modified 3 wire SI's and have heard the same problems as previously posted
Should there be a fuse in the wire that goes to the Battery? If so how many amps? Less than, more than or equal to the alt max?
They all look the same from the outside, the difference is internal. Some builders if one wire alternators install a plug on the twin spade terminals to identify them, but others don't. The original application for the one wire regulator was marine and industrial use, where there was a minimum amount of wiring in the whole system. The regulator looks exactly like the normal one, outside of the part number on the outside.
Never seen anyone successfully put one in. The main "battery" wire should go directly to the battery lead on the starter. Not through the harness.
The main charge wire should be 10 guage or bigger. I didnt run a fuse, dont believe 'factory' installations had one, but a big amp breaker or fuse wouldnt be a bad idear either. 120 amp or at least as much as the alternator puts out anyway. Some newer cars and imports have the alternator fused, usually found in the engine compartment fuse box, maybe grab one from the wreckers if you want to run one.
I been having fits with powermaster 1 wire altenators, got 2 of them draining batteries on different cars. There might be an internal diode that burns out if you don't follow a procedure when disconnecting the battery. I just leaned this from an electrical engineer that i had sent one of the altenators to (he left the shop about 5min ago). I don't know how good or if he is right, he gave me a bunch of advice and criticized how powermaster made the altenator - but he never fixed anything. Hope you have better luck than i.
Cool, I was hoping it was three for the reasons that El P mentioned above. I want to have the idiot light and from what I understand it only takes 2 more minutes to hook up the other wires. I just couldn't find any good photos. I can obviously see three wires but I didn't know if they only counted one on the pigtail if the other was a ground or something...I'll get the wiring diagram from the thread I found last night. Thanks.
In the photo above, the jumper wire is routed to the main hot lead of the alternator. In practice, this is often done and there usually is no problem with it. However, the factory runs that wire right back to the battery. But isn't it electrically the same, regardless of where that wire picks up the +12 volt connection from the battery? Yes, and no. Electrically, it is the same and in fact, the larger the gauge of wire you use from the battery to that main hot connector, the less of a difference there will be. That little wire is what is reading the battery voltage. Said another way, the regulator inside the alternator uses the voltage that that wire sees to determine how much juice to put out (needs to know when the battery gets up to nominal voltage). Not too much current flows through that wire, so it does not have to be too big, but we also don't want a big voltage drop across that wire, so it can be bigger gauge than what you would size it with based solely on current draw. In practice, the regulator gets a better picture of what is going on if that wire goes right back to the battery. Again, the expedient is to wire it as shown. And again, in practice this does not work badly at all. But now you know the story of what that wire does on this type of alternator.
I always wondered why GM went to the battery with that wire when it could have been connected an inch away. Good info to have.
Most factory alternator output wires have a fusible link in them; looks like wire, but it will sacrifice itself in overcurrent situations. Was he saying it would burn the diode if you disconnected the battery while the car was running?
Fusible link you say eh - interesting, never noticed that. What current rating would those be then - I think those fusible links are rated by gauge aren't they? Sounds like a possible wiring revisit for me anyway.
Yes, and that kind of shows how important it could be. No way the automakers would spend more pennies on a longer wire if a shorter one would do.
You are correct on all counts. There is an increased chance of overcharging the battery if you hook up a three wire alternator in the way shown in the lead photo in this thread. One wire alternator voltage regulators are calibrated a little differently, and supposedly that accommodates the IR (or voltage) drop seen in the one wire. However, in an aftermarket configuration, there is no reason to expect that you will hit the nail on the head in terms of the resistance of that large-gauge feeder wire. One wire alternators are cleaner installations, of course, and on an occasionally-driven car like rod you probably do not have to worry too much about overcharging the battery, since it probably goes flat on you anyway from extended storage. (we DO all use Battery Tenders, now, don't we?) And you are right that the other wire can just go to the idiot light instead of a diode. For that other poster, a blown diode is usually an open circuit, so you are not going to drain a battery through a blown diode. I don't remember ever seeing a diode that failed by shunting (acting like a clsed switch).
heres what i do right or wrong, no problems ever. i just run a jumper from the #2 terminal to the bat. terminal, then the main charging wire from the bat. terminal to the battery.
The purpose of the of the smaller wire being hooked to the key for a 12volt source was the turn the alternator off other wise the diodes and rectifier bridge stays hot all the time and can cause battery drain over a period of time not to mention shorting alternator life. The way the Idiot light works is when the key is" on" and the alternator is not turning or not charging the #1 terminal acts as a ground and the Idiot light is on.voltage is also flowing from the key to the "R" terminal and suppying power to the rectifier. Once the alternator is charging the # 1 terminal starts to put out low amp voltage.you then have 12volts going to #1 from the key and 12 volts coming out of #1 from the alternator there is no ground so the light goes out. The big 10 gauge wire is the is the high amp output and is just a source to get the juice produced by the alternator to the Battery. Hope this helps
Yes, fusible like is rated by gauge. In this application, 12 to 14 gauge will do the job depending on how many accessories you are running. This would also equal the equivalent of a 50 to 60 amp Maxi Fuse, which I would recommend the Maxi fuse as it's easier to replace rather than crimping on a new piece of fusible link and ultimately shorting up the wire going to the Alt each time you have crimp on a new peice.
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