XJ750 Seca Charging Issues

So much to my frustration, the charging system just won't charge...

I have looked at my manual and a lot of specs online and here is what I know so far:

- My rotor measures around 4.1ohm between the rings on the face, but at the brown and green wires (at the plug) the resistance is only around 1ohm.

Definitely has power to the field coil.

There is no continuity between the white stator wires and ground. And measuring between these, they are all within spec.

It has new brushes and the brown and green wires from the brushes to the reg/rec are continuous with no breaks. The plug has been cut off and it is currently wired using terminal blocks.

I have even tried holding the brushes against the face of the rotor - no change...

Experts, please help!!

 

While it was running? It has to be spinning to make charge voltage

Did you get the M unit installed and now this is an issue? Double check you have all the wiring in place

 

No, I was hoping the ohm reading of the rotor surface would translate through to the green and brown wires through the brushes - not looking for voltage at this stage, just troubleshooting the components.

This was an issue pre m unit but it's all on and running.

I spoke to motogadget and they advised to wire the charging circuit:
- whites together (stater to RR)
- green together (regulated)
- red to battery direct
- black to ground
- brown to key +12v

All these wires that are supposed to have voltage, show +12v. Just nothing changes when the engine is switched on...
-

 

Update: after thoroughly polishing the rotor face, cleaning and swapping brushes I now have:
4.4ohms on the rotor face and
4.7 ohms at the brown and green wires.

I understand this is out of spec.

Would people recommend a new set of brushes or rotor and brushes together?

 

Put the probes together to check for resistance in the meter and subtract that from the figures you have.

 

New brushes if the bike has quite a few miles just because Yamaha spec'd them at around 10,000 miles.

Also like Franz suggested, and then measuring at the brown and green wire is typically a bit high, but normally does not cause an issue. I think I read close to 12 ohms on my 750 there and the charging system is fine.

What is the voltage on the green wire with the bike not running and the ignition switch on? Does the field coil (rotor) produce a magnetic field in this condition - use a thin feeler gauge next to the cover and it should pull in when placed close to the cover and the ignition switch is switched to on.

 

Yep, 0.8 ohms taken away from my readings.

I have 12v when measuring between the brown and green. This is a clean 12v switched from the m-unit. I will do the feeler gauge test and see how it goes.

Tha K you for your replies.

I am beginning to think it's the regulator...

 

Appreciate the help so far...

Okay, key on and using a thin steel feeler gauge around the alternator cover and I get nothing.

I definitely have 12v at the green and brown wires and when I probe the brushes directly.

What's likely the cause here? Wiring is continuous. I purchased a good used brush holder just incase, and no difference.

 

The green wire is the control wire, and should be close to 1.8V with just the key on and the bike not running. Therefore, there is an issue with the regulator or how it is wired. You need to have the brown wire (switched 12V) connected to the regulator as that is used as the sense wire.

And with 12V on both side of the brushes that means no current through the field coil and subsequently no magnetic field.

 

Thank you, your experience is greatly appreciated.

I most certainly have the same reading 12.8x volts on both the green and the brown.

Am I missing something regarding the Field Coil?

The green and brown wires go to the brushes...this may be a silly question but how does the current get to the field coil? Through the commutator rings on the rotor?

I most certainly have the brown from the Field Coil connected to the brown on the regulator and a switched 12v. The green from the coil just goes direct to the green on the regulator and no where else.

 

No silly questions - the current through the field coil is supplied by the brushes and controlled by the regulator. One side of the brushes (brown) is connected directly to the 12V switched. The control line (green) connects to the other brush and the Regulator varies the voltage on that pin to control the current in response to the sensed output (brown). If the green wire is staying high and the connections are correct then a bad regulator should be the cause.

 

You have been very helpful. I have two of the same $30 OEM equivalent"eBay" regulator rectifiers with both the same symptoms. I am going to suck it up, order a ricks or similar and report back.

Thanks again.

https://ebay.us/m/DwlP05

 

This was a long discussion, but turned out to be bad regulators, and the aftermarket didn't fair so well

https://www.xjbikes.com/forums/threads/1983-xj900-not-charging.132038/

The are actually pretty easy to bench test, which is discussed in that thread post 24

 

Wow reading that and sounds identical. Have ordered a reputable aftermarket replacement from a brand called "Arrowhead". Fingers crossed.

Link included as reading the XJ900 post, I wish he had included the link to the one that worked for him!

https://www.australianmotospares.com.au/products/aa-ams02-6-23058024-qty-1

 

Update: might be time for a bench test.

New "branded" regulator fitted.

Still the same result unfortunately.

No magnetic field - failed "slap test"

Red - 12.75v
Brown - 12.71v
Green - 12.70v

Green disconnected from main harness, I have 2.13a when grounding green from the brushes to the battery through the DMM.

Frustrating...

 

Update 2:

Could I please confirm something:

When the brown wire is not hooked up a switch 12v source, when I probe it with my DMM, black ground direct to battery, I get a reading of approx 9.2v, and when I probe it, it starts coming down quite rapidly.

Green wire when probed behaves the same way with the same voltage on it.

 

Not sure exactly what you have there but if it is still in the bike and all you have done is pull the switched brown wire from the main harness connector and then measured on the regulator side at the brown wire I would expect pretty much a zero voltage. Perhaps if as stated and the red wire is still connected there is some reverse leakage on the diodes that might show when using a DMM with a high input impedance. Other than that I could only speculate bleeding of a charge inside the regulator.

 

Hmm yes it did seem strange, but I still have a lot to learn.

Correct all other wires still connected, when installing the new regulator I simply forgot to install the switched 12v into the terminal and when I went to check I noticed what I described above.

So with the Chinese regulators, when the brown is not connected to the switched 12v there is 0v measured between ground and brown wire.

With the new "branded" one, when measuring either green or brown, without a switched 12v source, the multimeter reads around 12v initially then after about 1min of measuring, it will have run all the way down to 6.65v and it then stops there. This is on either green or brown only. The red wire is always constant 12.8x or similar as per the battery.

I appreciate your help so far Rooster. I'm tempted to make a video to better show what's going on.

 

For anyone still following along at home. I quickly put together a video to describe what is going on.

I am also sourcing the original regulator rectifier from the parts bike that the stator and rotor came from...