horizenjob wrote:
Running the car and charging it's battery are two different things. My formula car does not have an alternator. It will run until the battery goes dead and then it needs to be charged again. At some point along that path it will still run, but wouldn't be able to start up again because the battery would no longer have enough power, it just has enough power to run the ignition coils. Why? Well batteries are imperfect real world devices, you cannot remove the last 10% or it's power at the same rate as the first 10% of it's charge.
The alternator has two sets of windings in it, the rotating part on the stator and a stationary part that generates the magnetic field. The voltage regulator determines how much current is applied to the field which determines the output of the alternator. A small current in the field will cause a large output from the alternator.
Your symptoms of a car that will start and run, but not restart indicate the battery works and can deliver a large amount of power to run the starter motor, but it is being depleted while running. This points to the alternator not producing a charging current, most likely because the field winding is not being energized by the voltage regulator. It's possible for alternator to fail in other ways too, for instance they contain diodes, internal wiring and brushes that could fail.
In order to charge the battery you must overcome it's natural voltage and force current thru it the opposite direction to run the chemical reactions backwards from the way they do when the battery is discharging. So to charge your battery you must run at least 13V or 14V, the higher the charging voltage the higher the current.
A simple multi-meter is your friend here. Measure the voltage on your battery terminals when the car is not running. Then measure it again when it is running at idle, then at something like 1500RPM or 2000 RPM. If the voltage is less than when the car is off, it indicates the battery is being discharged - it's voltage is a bit lower because of the load it is driving. If the voltage is higher than when the car is off that indicates your alternator is being asked to charge the battery from the work of starting the car and running it.
When you get to this point you can be certain you have a basic diagnosis. I hesitate for you to just be connecting things until you get this far.
Next to understand is your alternator connections, it should have 3? There are large connections for ground and power output. Power output is many Amps, something in the 40-100 range. There should also be a smaller connection for the field windings which would be driven by your ECU/ELD combination. Lets' go over that after you do the measurements mentioned above. This will all make sense to you if we go one step at a time....
Marcus, I have just a small correction. I believe that you are mixing alternators with generators. In the alternator, the rotating part (rotor) is the one that makes the field and the stationary windings (stator) are in the case of the alt and provide the output. But besides that, you are correct in that the regulator controls the field and the field is used to control the output. Everything else I agree on.
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Chuck.
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The diagrams of alternators look sort of the other way but it's just the way they need to be drawn... 
) there has been a lot of great alternator diagnostic and hook-up info posted on this thread. I'm going to save a copy for when I wire up my alternator. 