Voltage Regulator/Rectifier

[neJeff]

Been dealing with known charging issues for awhile. The light/charging system has worked on and off but I recently took cover off the alternator to have a look and tightened up a loose bolt I found, since then I get nothing in the charging arena. Put a different used reg/rect that was supposedly tested and it did nothing. Re-checked the field coil and stator for ohms and again it is in spec where it should be. Guess I need another reg/rect. I did the off the bike ohm test for the reg but I get no change in reading on my multimeter for either one of these. Any other test before I purchase another bad unit

[bikerphil]

Any other test before I purchase another bad unit

If you tap into the green field coil wire and run it to ground, it will temporarily bypass the regulator and will help you determine if it is at fault. This should not harm anything if done for just a short period of time. Rev it up to 3-4K and check your voltage at the battery, should be nice and high at 14-15 volts. HTH

[neJeff]

Ok, this is with rect/reg disconnected I take it? If the green wire trick works it means for sure the reg/rec is bad?

[neJeff]

Sorry, leave it in place and rig a wire to it and ground it. Re-read it...

[bikerphil]

Yes, don't disconnect anything, just tap into the dark green wire that runs down to the alternator and ground it. See what your voltage is at the battery.

[neJeff]

I will do it today and see what's up...report back tonight Thanks Phil

[neJeff]

Ok, did the test and I get no change in voltage. Now what...

[cywelchjr]

Based on that you tightened the bolts on the alternator, and it quit working, even though the readings are coming out right, something got damaged or out of place when you did it. The field coil creates a magnetic field that the rotor "stirs" causing it to move in relation to the stator which is what causes it to generate power. That's not happening now. I'm guessing that for some reason, the field coil is not actually getting any juice. One check is to take a small metallic object (like a feeler gauge, thin and steel) and hold it by the alternator while the bike it running. If the field coil is working, then the feeler gauge will pull against the alternator. If it does, then the problem is connection to the stator in some way. If for some reason the rectifier portion of the regulator had gone out, that would explain, but that should show up in the tests in the FSM, and having two fail that way is unlikely. Oh, before going further, there are two wires to the field coil, make sure voltage is being applied to it, cause if no voltage is applied, the reg can apply all the ground it wants to the other side and nothing will happen.

[bikerphil]

Without unplugging the 2 wire field coil connector, make sure you have 12V at the brown wire with the key on. The voltage at the green wire should be less than 2V. Try these tests if you already haven't. Make sure your meter is set in the 20VDC range.

[vintagemcyclegu]

similar problem with 80 XS1100SG

I am working on a simalar problem with my 80 XS1100SG. No charging voltage and no headlight. Field coil 3.5 ohms, stator coil 04 ohms. Reg/rec gets really hot is this normal?. Also headlight does not work. changed headlight relay and check inline diode OK. Checked all ground contacks all are fine.

[neJeff]

Ok guys, I took for a ride and discharged it quickly...quicker than ever before. Key on volts at battery are 11.8, at brown wire 10.5, at green wire .98. What does this tell me? Thanks

[bikerphil]

Are you positive you have the .4 ohms at the white wires? if you haven't, unplug the 4 wire connector and check the 3 possible combinations between the white wires going to the stator. How did you make out with the feeler gauge test like Cy mentioned? The engine doesn't need to be running to see if the field coil is excited, just the key on.

[neJeff]

Yes, I checked them yesterday and underneath the tank also, meaning it was down the proverbial electrical line, and I just checked cover and it holds a small drill bit nicely.

[bikerphil]

Only thing left then is the battery might be NFG,

[neJeff]

Sorry but did we someone determine through all this that the voltage reg/rect is fine? Battery is 6 weeks old...