How to identify alternator pins without labels using ohmmeter or other means

Hello,
If I needed to test an alternator on the bench without having any information about it or any identification on it. How do I go about hooking up the wires to the brushes/regulator pins? How do I know what wire to hook up to where without colors, labels, and the like. I assume an ohmmeter is a good start or....?
There are typically three wires, that is for sure. One must be to the regulator itself... but which one?

How do I know which of the wires to hook up to where? Are they all hooked up to the battery or only one is the essential one beside the common ground which is the body of the alternator?

The output to the battery is of course too obvious to ask. However, I do assume that the output to the battery is from the stator after it has passed through the diodes which have been rectified from three-phase AC stator coil output and the return the actual body of the alternator.......ooh that is a long one.

Thanks in advance for any help.

Thank you very much.

Without ANY informarion you would be guessing and probably at a loss....

You obviously are talking about an alternator with an internal regulator. There are quite different arrangements possible, 2, 3, 4 wires. Many alternators consume around 4 to 6 amps when fielded., so you might want to look for a resistance measurement of 2 to 3 ohms between two of the wires. Even better you open up the unit and have a look at where the brushes connect to. When full-fielding the alternator you should at least be able to check its maximal voltage output.

Some 4 wire alternators may work with a pwm signal going from the alternator to the pcm informing the module what it is doing and another wire from the pcm to the alternator telling the regulator what the pcm wants it to do, this could also be a pwm signal. Having identified the field contacts you could try to fiddle with these command and control signals. Watching the alternator output while injecting signals into these lines you may get a clue what the design is or you may just burn something....it may depend on if these pwm signals are ground side or power side switched and wether the voltage is provided from the alternator or from the pcm.

Some three wire alternators also may feature pwm control on the third wire, on some it might be only a voltage sense, on others it could be a charging indicator control...

If you are not willing to reverse engineer these components it might make more sense to search some information about them before getting frustrated or burning them on the bench.

Thank you very much. I see the crux of what you have covered. Regulator, computer, and whatever else they sit around and come up with. No wonder why it is not this or just that.
Of course, a person who knows the basic principle of operation may decide to indulge and change the alternator and play around with internal mechanisms to serve his own little purpose but that is another subject. Thank you.

I was mostly thinking to do this. Get 3 phase AC from one. Remove the diodes, remove the regulator or one can simply install a variable resistor to change the value of AC output etc.
I was wondering what kind of 3 phase AC voltage a typical car alternator puts out if one place it up on the roof and install some blade and let the wind spin it. I assume the output would depend on the rpm.

I was turning a synchronous motor with magnet rotor. I noticed it was producing over 1000 volts 3 phase AC but hardly any amps at all. I guess them coil wires must be really really thin with lots of winding.

Thanks for everything and I enjoyed that last line of wisdom. Very humbling.

The problem with AC generation using a windmill or waterwheel is controling frequency this one of the reasons most off grid systems work at 12v DC where AC is needed it is converted to 60 or 50 hz using an inverter. Using 12v also makes the system compatible with sollar panels. Also where multiple AC generators are connected on the same bus load sharing and synchronization becomes an issue for example if you have two generators and they must be governed turn at the same RPM and be in phase or one will do all the generation and the other act as motor and just put additional load ob the system.

Thank you. It makes perfect sense and the issue subject you covered was appearing in my thoughts to the extent of the knowledge I had.
A question that I like light shed on and I am not clear on it as I like, is: In a car alternator is one of the brushes connected to its body either directly or through the regulator since to my knowledge the entire car is one way or another ( the other wire) the return wire. to complete the circuit.?

If that be the case then there should be some continuity between the two brush pins by some amount and the pins and the body of the alternator and then the coil ( the hot connect to the battery) and the alternator body. Everything is using the body as the return. But that won't make sense as that would drain the battery without any relationship to the computer drain etc?

The only thing that goes through my mind why it doesn't is because the battery's terminals are separate and any very small drain that would exist takes place inside the electrolyte ionic activities.

I probably am carried away and don't know what I am talking about.

Not sure if I understood your question but here is my take on it:

One of the two wires controlling the exciter current is connected to ground, at least temporarily. This happens to be on a ground side switched control design where the gound may be pulsed or resistance on the ground path may be varied to achieve the charging goal.
On a (positive) feed side controlled design you indeed have a permanent ground and your continuity tester should reflect this between the corresponding wire and a body ground. (Most probably both "brush" wires will show continuity as most testers won't show no continuity/high resitance until at leat 30 ohms, others may go as high as 100 ohms for not to show continuity.) Know your tools !

The stator part of the alternator is only related inductively (while spinning) to the armature side of the alternator.....and if you look at the B+post of the alternator you will find that it is isolated from ground by the rectifier bridge/diodes.

Once again, not sure if this adressse your question, though I hope it helps to clarify a bit.

T