Alternator Wiring Help

[Begle1]

I can't figure out my alternator. I rewired it and now it doesn't charge.

My understanding is as follows:

External voltage regulator:
Grounds to the firewall through it's case.
Receives a 12 volt supply from ignition switch (blue wire).
Outputs a voltage/ current to the alternator field coil (dark green wire).

Alternator:
Grounds to the engine with a 6 gauge black wire.
Connects to the battery positive with another 6 gauge black wire.
Receives a 12 volt supply from the ignition switch (blue wire). WHAT IS THIS FOR?
Receives the output from the external voltage regulator (dark green wire).

So it should charge as long as I give the regulator 12 volts, the alternator 12 volts, tie the regulator to the alternator, and hook up the main alternator ground/ positive?

Is there any reason why one of these alternators wouldn't charge through a solid-state battery isolator?

[Begle1]

Alright, I got it wired right, I see 14.4 volts through the isolator at each one of the batteries.


I don't know the details, but...

While the engine is running, if you disconnect it from the voltage regulator, or disconnect the voltage regulator from the 12 volt source, then the alternator puts out a high RPM-dependent voltage.

While the engine is running, if you disconnect it from the 12 volt source voltage, then the alternator stops charging entirely.

Disconnecting the alternator from either the voltage regulator or from the 12 volt source voltage does not stop alternator-based tachs from working.

So the right way to wire an alternator kill switch would be to interrupt the source voltage to the alternator (blue wire). I guess that disconnecting it from the voltage regulator (green wire) effectively full fields it.

[Begle1]

Oh man, this is awesome. Now all of a sudden, my rear battery is charging at 27 volts at idle, while the front battery is sitting at 8 volts.

Oh, and apparently my starter is sticking on now too.

For some reason it is impossible for me to actually get voltage to the KSB.

Shoot me.

[PToombs]

Well, ok, it is turkey season here!

[Begle1]

With the starter stuck on I managed to drop a 1000 CA Optima red-top down to .268 volts... I didn't even know it was stuck on since it wasn't even making any noise at that point... But the battery shot back up to 4.5 volts after I turned off the starter, so it's gotta be good still, right?


Seriously, I don't get it. The voltage regulator has source voltage. The alternator has source voltage. The voltage regulator is putting 1.2 volts to the alternator. I've totally removed the isolator and second battery from the system, still no charge.

What kind of range should the regulator be putting to the alternator? Or should I be looking for current?

I don't think that the rear battery was charging any more than the front, I think that the voltage reading at that battery is thrown off by the giant capacitor in the inverter on that battery. So I think that the alternator is just not charging at all. But I don't know why.

[Begle1]

I FIXED IT I FIXED IT I FIXED IT!!!!


The green wire going to the alternator is from the voltage regulator. From what I gather, the voltage drop across the field coil is the 12 volt source voltage from the blue ignition wire, minus whatever voltage the green wire has. Typically that green wire has 5 to 7 volts it seems, so that there is around a 6 or 7 volt drop across the field coil. For whatever reason, my voltage regulator was putting 11.5 volts to the alternator, so it was hardly charging at all. I replaced the voltage regulator and all is well.

Last time my regulator crapped out on me it decided to not put any voltage to the alternator, which full-fields the thing and is how you get the alternator to put out 30-50 volts. This time it decided to just put too high a voltage out, so apparently they can fail in two different ways.

Good thing I steal voltage regulators from junk yards.