Overcharging Issue

[CodyLane]

Hey Fellas, I've got something that's got me puzzled. I've been having charging issues with my XS11 lately. At first it was low voltage (barely over 12v) and after cleaning everything up and my voltage climbs steadily up and up and up and doesn't want to stop. I installed a voltmeter to monitor the charging system. First ride on the freeway and it hit 17.9v. I've gone through and cleaned my grounds and connectors, I've replaced the voltage regulator (with no change in symptoms) and I'm just stumped. Any of you wizards know why if I hold it steady at 3000 rpm or more, the voltage climbs so high?

[BA80]

Hey Fellas, I've got something that's got me puzzled. I've been having charging issues with my XS11 lately. At first it was low voltage (barely over 12v) and after cleaning everything up and my voltage climbs steadily up and up and up and doesn't want to stop. I installed a voltmeter to monitor the charging system. First ride on the freeway and it hit 17.9v. I've gone through and cleaned my grounds and connectors, I've replaced the voltage regulator (with no change in symptoms) and I'm just stumped. Any of you wizards know why if I hold it steady at 3000 rpm or more, the voltage climbs so high?

The regulator controls the voltage. That is the ONLY thing it can be.

Unless, your VOM is fruit. Try another meter and see if it reads differently.

[CodyLane]

I thought maybe the VOM was reading inaccurately but I tested with a multimeter simultaneously and got the same readings. Initially I thought the voltage regulator was toast, that's why I replaced it. It'd be pretty unlucky if my replacement also was toast. I guess I'll have to try another regulator. Thanks for the help.

[bikerphil]

Check the resistance of your field coil, if it is shorting to ground, you will get full voltage all the time.

Edit: Reading should be 3.5 ohms at the 2 wire connector (brown and green wires)

[CodyLane]

Thanks Phil, I'll take a look at that. Perhaps it's shorting out somewhere in the harness. Probably where the clips hold it in I'd guess.

[bikerphil]

Yep, I know by shorting the green wire to ground will jump the voltage up as if there were no regulator, I have done this in a pinch to get the battery to charge with a failed regulator.

[DiverRay]

I had my '79 short a wire inside the harness, and it caused an overcharge. I ended up taking apart the section from the RR to the front of the frame to fix it. It was a HOT lead that shorted to a ground wire, but not quite a direct short...

[CodyLane]

So it looks like I might have found my problem. I bought myself a better multimeter because my other one was ****e and had very inaccurate resistance measurements. Tested the resistance of the field coil and it was low at 2.9 ohms. After pulling the stator and field coil assembly apart, the field coil tested at 3.6 ohms. Turns out that one of the bolts that held the field coil on the side cover was waaayyy too long and had actually pushed up and into the field coil itself. Funny thing is, I have never touched those bolts so it seems time, heat and vibration finally caused it to rub through or something.




Looks like it was shorting directly from the coil to the case. I put everything back together and tried to get it working but after that bolt was removed, the field coil wouldn't generate a magnetic field. I tested the brown wire and was getting 12+ volts so I think it was relying on that embedded bolt as part of the system. Looks like I'm ordering a field coil now....
Thanks for the help guys!

[BigRed]

32 ohm field coil resistance?

I've been trying to chase down an overcharging issue as well. My bike runs around 15.7V.

I found this thread, and tested my field coil resistance. Rather than the 3.5 ohms mentioned above, I found 32 ohms across the 2 wire connector. Does this mean it's time to pull the field coil? I would have expected a failure to result in less resistance; not more.

Thanks,
Brian

[3Phase]

I've been trying to chase down an overcharging issue as well. My bike runs around 15.7V.

I found this thread, and tested my field coil resistance. Rather than the 3.5 ohms mentioned above, I found 32 ohms across the 2 wire connector. Does this mean it's time to pull the field coil? I would have expected a failure to result in less resistance; not more.

Thanks,
Brian

Brian,

It sounds like the voltage regulator failed or shorted but since you've changed the engine and possibly the electrical system, instead of putting on my Karnak turban and channeling Johnny Carson I'll just ask:

Is that 32 Ohms measured at the regulator/rectifier across the Brown and Green wires on the harness side of the 3-pole connector with the Black, Green, and Brown wires in it?

Is the 3-pole connector connector unplugged from the regulator/rectifier?

OR

Is that 32 Ohms measured at the right-hand side cover connection across the Brown and Green wires on the alternator side of the 2-pole connector?

Is the 2-pole connector unplugged from the wiring harness?


Did you keep the XJ11 alternator that might have come with the XJ11 engine or did you remove it and use the XS11 alternator?

If you kept the XJ11 alternator did you use the XS11 regulator/rectifier?

The resistance values in the tests of both alternators are almost identical and will go higher or lower depending on what's installed, what's wrong and how it got that way.

[BigRed]

Thanks for the reply, 3-Phase.

I measured 32 ohms across the field coil from the brown and green wires on the alternator side of the 2-pole connector located behind the fuse block while the connector was unplugged from the harness. I was replacing the melted 3-pole (white wires) connector from the stator, which was also unplugged at the time. While I was in there, I also applied dielectric grease to the other connectors in the area, and I didn't notice anything obviously wrong (aside from the melted 3-pole white wire connector... and one of the wires had burned through its insulation -- these issues were fixed while I was in there).

About what charging system I've got -- I don't know! I didn't swap the engine... the bike came to me like that about 15 years ago. I only discovered that I had a frankenbike while I was chasing down ignition issues many years ago. I know the ignition side of things (pick up coils, etc) belongs to the XS rather than the XJ, but I do not yet know if the charging system was also swapped, or even if there is any significant difference between the XS and the XJ. If there are differences between the two charging systems, how do I identify what I've got?

Thanks again,
Brian

[3Phase]

Right on, you tested only the field coil and not the field coil + voltage regulator + entire Switched Power distribution from the ignition switch Brown wire.

Look at the alternator cover and if it sort of sticks out in the middle and has YICS cast into it then it's the XJ11 alternator:-

[BigRed]

Yep... that's what I've got. Looks like I've got more homework to do.

Would you happen to know what testing I should do for an XJ charging system that is over-charging? I'm happy to try swapping out the reg/rect if that is a sensible first step. Well... second step... I've already cleaned up and replaced bad connectors.

Thanks,
Brian

[3Phase]

I think there is a short in the Green wire to the voltage regulator or the voltage regulator itself blew out and shorted to ground. Grounding the Green wire anywhere in the circuit basically full-fields the alternator.

Since you have an XJ11 alternator it should have a Green wire and a Black wire for the field coil 2-pole connector. Check the resistance of the Green wire to ground, then check the Black wire to ground. If the Black wire is shorted to ground that should actually blow the 30A Main fuse, not overcharge the battery but you never know.

If the field coil wires are not grounded, unplug the regulator/rectifier and check the Green wire in the harness-side 2-pole connector wire to ground. Go ahead and check the Brown wire to ground but if that was shorted it should blow the 30A Main fuse, not overcharge the battery.

If the wires are not grounded then the voltage regulator is bad and has to be replaced.

The high resistance in the field coil is likely dirty or worn brushes and slip rings in the XJ11 alternator:-



I don't have a picture of the XJ11 regulator/rectifier but you can find one on the 'net somewhere if you need it. You probably have the stock XS11 regulator/rectifier with the rectifier 3 White wires, 1 Red and 1 Black wire in the same 6-pole connector. The voltage regulator connector has the Brown and Green wires in the 3-pole connector:-

[BigRed]

Thanks so much for that very comprehensive action plan. Now I know what I'm doing tonight!

Brian