I know this is beat to death but i am having a charging issue I do not understand.

[rshelbert]

Ok in the charging troubleshooting steps in the tech section I was performing the tests and I am confused. !st of all i got a good rotor from a friend, originally it had none.

81 xs motor with stock electrics

I tested the feeler gauge with the ignition switch on, It had very weak magnetism.

I grounded the green wire and volts were going up but not much, about 13 volts was all I could get. I ordered a new set of brushes, installed them and cleaned the rotor well. This resulted in same no magnetism but with green wire grounded 14.8 volts solid.

As per the guide it points to a bad regulator/rectifier. But I went ahead and decided to test the rest of the system for the hell of it, and this is where I am confused.

I tested the stator output and I read 0 volts AC between any and all white wires. The resistance between any and all is about the correct .5 ohms. None are shorted to ground.

My confusion is if I am receiving 0.4 (or essentially the same as if i connect it to my finger) volts A/C on the white wires between any 3, where the hell am I getting the 14.8 volts dc when I ground the green wire. I have to be doing something wrong, but I am unsure as to what.

Any insight would be great and thanks in advance,

Rick

 

[TwoManyXS1Bs]

While you're testing a white-to-white a/c voltage, temporarily ground that green wire, which would energize the rotor, and should cause the a/c voltage to come up...

 

[rshelbert]

Hmm that makes sense, I did not put that together until you mentioned it. I will check that out tomorrow and see how it goes. Thanks for the insight.

 

[TwoManyXS1Bs]

The following is an excerpt of XSLeo's post in this thread:

http://www.xs650.com/forum/showthread.php?p=360508#post360508

Leo has an understandable 'everyman' form of expression, so I've taken the liberty of cleaning it up as a simplified "Theory of Operation".

The regulator regulates voltage. The 14.5 is volts. Current is amps.
Diodes are a one way valve for electricity. The rectifier is a series of 6 diodes arranged so the AC can only flow one way, DC.
If you google rectifier you will get a better explanation.

(For 80-83 charging systems)
The brown wire supplies the current through the rotor to create the magnetism the rotor needs to have. On the rotor one end becomes the positive pole of the magnet, the other end negative. Looking at the side of the rotor you see triangular shaped pieces of steel. Some point one way, some the other. These are part of the rotor ends, this makes four of these positive and four negative. They alternate positive and negative (or North and South).

In the stator are 12 windings. These are arranged into three groups.
Now as the rotor turns a positive triangle passes one of these windings. As it passes it creates a positive current in the windings.
Then, a negative triangle passes the same winding. This creates a negative current flow in the winding.

This happens in all three groups of windings at the same time. Each group of windings are set up to be 120 degrees apart, so you get three sets of voltages coming out of the stator 120 degrees apart, thus the term three phase.
These voltages come out the three white wires. In three phase AC. These white wires are hooked up to the six diodes that convert the AC to DC.

The brown wire supplies the current flow through the rotor. The regulator controls the ground for the rotor. When grounded the current flows through the rotor. This creates the full output of the alternator. This full output charges the battery. When the battery reaches full charge it ungrounds the rotor.

Once you understand just how this works it demystifies the whole thing. Makes it simple.
Knowing how it works makes it easier to figure out what's wrong and fix it.
Leo

 

[rshelbert]

Just a followup on my problem for people who see this problem in the future. As stated above when the green wire was hooked up to ground the AC voltage was accurate.

The rectifier/regulator was in fact bad, The troubleshooting guide in the tech section was accurate on identifying the problem. I replaced it and the system is charging perfectly now, about 12.4 or so volts at idle and about 14.3 to 14.5 at 3k rpms.

Just do not try to check AC volts to test the stator if the rotor is not energizing, it will not produce any volts. The resistance checks will test out just fine.

Apparently either the rotor went bad at some point in its life and took the regulator/rectifier with it or vice versa. I am not sure to which but the rotor was missing when I got the bike so it was probably the culprit.

I am ready to hit the road now so thanks to all for the help.