The Stovebolt Site Forums The Shop Area The Electrical Bay 12 Volt Alternator Issues.

I just finished wiring what was left of the uncompleted rewire project. Got light!! Thats a plus. But they are dim. I went and checked the battery while it was running and not happening. So I went to the alternator itself. Attached it a link to a picture of it.

When I test the two wires coming out of the plastic plug while it is running, the red wire has no juice. The yellow wire has juice, but it is not connected to anything. I had posted about the yellow wire before and was told it was just an idiot light connection.

Questions

Shouldn't I be getting a voltage reading at the connection to the small red exciter(?) wire when I run the engine with yellow wire and red wires unplugged?

Can someone tell me how to tell if my alternator is making electricity?


Heres a better link

http://img.photobucket.com/albums/v617/daniel1060/46GMC062.jpg

How about the big one at the back of the alternator? It's supposed to be connected directly to the + terminal of the battery, either through the ammeter, or directly to the battery cable at the starter. Since the red wire goes out of sight, is it safe to assume it's looped from the large terminal at the back? If so, figure out why there's no battery voltage at the big lead. You'll never get any charging current unless that one's connected properly.
Jerry

The big red wire goes to the amp guage then it feeds to the light switch and ignition.

Can I just run a wire direct to the battery from the big red connector? Will that make it charge?

Put a voltmeter to the terminal at the back of the alternator. There should be 12 volts there at all times. If that one's hot and the small red lead is connected to it, you've got a bad alternator. It doesn't matter where it's connected, as long as it is able to put a high current into the battery. Yes, a wire directly to the battery will work, but the ammeter won't indicate a charge if you do it that way.
Jerry

Will the red lead be hot even when the motor is not running?

Its hot. With the motor off. So are you saying that indicates a bad alternator?

Yes. If the wiring is done properly, there will be a #10 or bigger wire from one side of the ammeter to the battery cable terminal at the starter. The other ammeter terminal will have three wires, one to the ignition switch, one to the headlight switch, and another to the alternator. There might also be one to the fuse box for a total of four wires from one side of the ammeter. These wires should be hot all the time, ignition on or off.
Jerry

Yes, assuming the small red wire is also hot. There could be a bad internal regulator, but rebuilt 10SI alternators are so inexpensive it's foolish to try to rebuild it unless you've got all the parts lying around at no cost.
Jerry

So I found some wiring descrepacies with what the dude did and what it says to do in the instructions. There is one red number one wire that goes to the amp guage. There is another one with a pigtail . I assume this is the ignition to light switch that is at the top of the page.. The problem is the lead doesnt reach the light switch. So he had the taped lead going to the amp meter and ignition. But still I only have two wires to the amp meter.

These are my instructions.

http://img.photobucket.com/albums/v617/daniel1060/46GMC064-1-1.jpg

A #1 wire would have a copper conductor as big as your index finger. Maybe you mean a #10? That's about right. With a #10 from the ammeter to the battery cable at the starter, and another one from the other ammeter terminal to the back of the alternator, you should be getting a charge, as long as the small red wire in your picture is also connected to the big terminal at the back of the alternator. If those connections are made and there's battery voltage at the back of the alternator and the small red wire, change the alternator.
Jerry

No the number one wire I was referring to was the one designated number one in the wire harness instructions.

Thanks, Jerry. I'll get a new one and go from there.

ALL RIGHT!! Got it in today and all is well with the charging. Bad alternator. Thanks for helping me through this. Now on to resolve the gas gage issue.

"I love it when a plan comes together!" Good show!
Jerry

This is pretty simple.....The yellow wire goes to the (+) terminal on the ignition coil and is known as the exciter wire. It is the one that tells the alternator to go to work when you turn on the ignition key. The short red one needs to go to the 10/32 BATT stud on the back of the alternator and that is for the internal regulator to tell it what to do. Finally you should have a 10 gauge wire going from the BATT stud on the back of the alternator up thru the amp gauge then over to the starter solenoid where the battery cable connects. That will deliver the output from the alternator to the battery to keep it charged up....and you will live happily ever after. Randy

Ok here goes...The yellow wire should connect to the (+) terminal on the ignition coil and has the job of turning on the alternator when you turn on the ignition key to make it begin to charge. The short red wire in the plastic plug connects to the 10/32 stud on the back of the alternator marked BATT and is for the internal regulator so it knows what to do. Finally you should have a 10 gauge wire from the 10/32 stud on the back of the alternator that runs up thru the amp gauge in the dash then on over to the battery post on the starter solenoid. that is how the output from the alternator get to the battery. Do this any you will live happily ever after.....Randy