Charging system problem

At the alt battery terminal I have 12.30 something.

 

Ok, with the Engine running, what is the voltage at the stator terminal (white with black stripe wire) on the back of the alternator?

 

I have no access at all to the stator wire. Ti tight to test while mounted.

 

Ok, no prob.

With the engine running, what is the voltage of the F terminal on the voltage regulator?

 

F and S give no reading.
A and I have the same 12.38 reading.

 

Ok, without the engine running, what is the voltage at F?

This should be the last measurement.

 

F has no reading.

 

F did not give a reading with engine on or off.

 

Sorry, I meant to say unplug F and take the voltage reading on the F terminal of the voltage regulator (key ON, engine OFF), sorry about that.

 

I dont get a reading.

 

Ok, I suspect the voltage regulator. You either should replace it again (they have been known to be bad out of the box) or try a known good voltage regulator.

The F terminal is the field terminal for the alternator. It should be greater than 0V to initially excite the alternator, then it switches to 12V once the alternator is generating. The voltage regulator dials that down to control voltage output.

 

Would the voltage regulator make the alternator make a whining noise?

 

It could. If the field is shorted to ground inside the voltage regulator, any residual magnetic fields would induce current into the field windings and go straight to ground.

You could verify the short: Unplug all the voltage regulator connections. Change your voltmeter to measure resistance (that symbol looks like a set of headphones). Measure the resistance of the F terminal relative to ground.

 

This my 3rd voltage regulator.

 

Interesting.

What brand and supplier?