I'm back with more questions about alternators. Is it safe to say that all GM 10 SI models are interchangeable in the sense that they will plug in and and work in any car that had a 10 SI to begin with. I know that they have different outputs and that a lower amp model may not keep up with demand but will it function? I'm just trying to understand how they built cars back in 1972. If so, is the same true for swapping one 12 SI for another ? Can you upgrade from a 10 SI to a 12 SI by simply swapping alternators or is there more to it ? Last question. In my 72 Skylark, is the voltage output of the alternator controled within the alternator itself and if so is the funtion of the external voltage regulator just to direct or route the current to differnt parts of the electrical system as needed? As you can tell I'm confused about what "internally regulated" means.
All 10/12 SI alternators will interchange depending on "clock position"of the plug for mounting.72 was a split year,some early cars had firewall regulators,later models had the internal 10SI.In either case the regulator is the "brain"of the charging system.When running the alternator output is directed to the load demand,any excess goes to the battery untill it is at full reserve.An alternator is not a battery charger as many people think.:Smarty:
Actually, the alternator IS the battery charger. It is also intended to supply the current the vehicle needs as well, which is why the regulator is needed. The alternator is a constant output device, unless something controls it. When the current demand is high, the alternator's output is full, and the demand either exceeds the supply, or nearly so. As the current demand diminishes, either through turning off components, or as the battery charges, or both, the alternators current output becomes a voltage output, which continues to rise to the regulator point. At that point, the high voltage tells the regulator to dial its output down to maintain "sanity" in the system. Many high output alternators can put out 24-28 volts, if unregulated. That is why it is called a voltage regulator. The alternator IS the battery charger, and is controlled by the regulator. Class is dismissed. Ray
Internally regulated, as opposed to externally regulated, simply means that, if internally regulated, the alternator will have the regulator installed in its case. Externally regulated means that the regulator is a box on the firewall. Output is simply designated in current output, in amps, and determines how much of a load can be maintained by the alternator before the battery starts supplying current. The higher the output in amps, the better at maintaining the system is at maintaining a charge, and supporting the vehicle without turning to the battery. With respect to output, the regulator will control the alternator's output by controlling its voltage. There are VERY few situations where the alternator is simply too big. In this case, more is better. Ray
Good, this is the type of info that I'm looking for but I have more questions. My 72 does have a regulator on the firewall. So does that mean that the alternator simply looks like a 10 SI but is actually another model ? Also, the Buick shop manual says that all cars with a 63 amp alternator had a special diode on the voltage regulator. Why did only on the 63 amp models have this diode ? And last, when I go to the parts store and ask them to look up a replacement alternator for a 72 Skylark or a 72 GS 455 the search comes up with a 100 amp 12 SI. If that is the only replacement they show, then what do I do with the current voltage regulator and it's special diode?
I think what Jamie's trying to say is that an alternator is not a battery charger when the load demand exceeds the alternator's output...in that case the alternator works its butt off, and the battery is at that load's mercy as well...until...the end. Devon
I thought I'd clear up why I'm asking all the questions. I'm swapping my 350 for a 455. As I do that I was thinking of doing it with all the accessaries in place. The 350 would be pulled along with the alternator, PS, starter, sending units hoses, belts ect. as one assembly and the 455 would be dropped in with all the same parts already attached but newer or rebuilt. The only thing that would be added after the drop-in would be the carburetor and exhaust manifolds. I'm certain about everything except the alternator and I don't want to cause any major damage to the electrical system. It looks like the safe thing would be to just keep the same alternator move it to the 455 and not worry about it until it dies. Ron
Well i stand by my statement,not here to argue with Ray. Your '72 alternator is a 1 year only 10DN in a 10SI case,i'm not suprised the parts house cant ID it.As for the diode,i remember hearing talk about it at a seminar years ago.I think it has to do with the A/C spiking the system during shutdown.GM didnt make the 12SI until the '80's,it was 56-66-78-94 amp...your parts house is probably trying to cover all these applications with a 100amp unit.
Well that clears up some of the confusion. I mean a 10DN in a 10SI case that was only produced for one year or less would not be something the parts counter guys would be aware of. I'm guessing that I won't be able to just drop in a 10 or 12SI model because the voltage regulator is already there on the firewall. Is that correct? I don't know how the internal regulator can do all the functions of the old voltage regulator with just three contacts but I maybe I don't need to know. Thanks for the information. Ron
When it comes to the engine size, the only difference electrically will be the size of the battery. A larger battery will require one of two things: A larger alternator will charge it faster, and a smaller alternator will take longer. Herein lies the rub, and I think this is where the "end" comes in. If a 60 amp alternator spends most of its time close to its rated output, the heat will quickly kill it. Under those circumstances, a larger unit will not only last longer, but will better meet the demand, and charge the battery faster. The alternator has two jobs: one is to meet the demand of the vehicle at its maximum demand, and to charge the battery. These can be seen as individual demands being met by the same unit. If the vehicle demands 60 amps at maximum demand, a sixty amp unit will burn up trying to meet the vehicle's demand, and still not charge the battery. An 80 amp unit will meet the demand of the vehicle, and have only 20 amps to spare for the battery. This might not allow sufficient time for the battery to charge, and the result will be a dead battery and a dead alternator. The simple fact: going bigger is ok, the bigger, the better. The draws will not change, but the alternator won't kill itself trying to meet them. The result will be an electrical system having more efficiency since both the vehicle and the battery will be happy. A note here: it is possible to retrofit a 10 DN with electrically larger parts. The problem is heat, and that is why the 12SI is used in place of the 10SI for outputs exceeding about 60 amps. The extra room allows more air to flow around the hot components, and is exactly why high output alternator components don't last in small cases. I could build a 200 amp 10SI, but the components will get hot enough to burn you, and the vehicle trying to meet the demand, should the need arise. I have seen these units hot enough to burn the belt off of the pulley. In this case, size matters. Your choice of going with the 12SI unit was a wise one. The adapter is cheap insurance. Ray
See this thread to learn what I learned when going to a 94 amp late '80s GM alternator; gain from my experience. You'll see a lot of the same guys providing great advice. http://www.v8buick.com/showthread.php?t=44117&highlight=alternator
