Charging system keeps failing

Hello Folks,

So Rosie's original alternator was "ohming" out of spec when hot, and was not putting out any more than 10.72 volts at any RPM and the battery kept dying.

I replaced the alternator, and voltage regulator with used parts that tested good. And she ran beautifully.

Today, my son calls me and says that Rosie is "dead."

Sure enough, battery is at 9.3 volts. When I jump it with another battery, she starts, and I measured the voltage across the battery and it 9.6 to 10.3 volts all the way up to 4000 RPMS. I ohmed out between the white wires on the alternator, and I am getting infinite ohms. So, I guess the 2nd alternator stator is "dead."

So, my question is, what keeps killing my charging system?

I have no accessories, other than front running lights inside the turn signals. 1157 bulbs.

I can buy a new stator, but I need to know what's killing them.

Thanks for any help,

 

Fully charge your battery right now.
What are the lengths of your brushes?? Do you see the wear lines?
Clean the brush contact surfaces.
Then test the rest to see what failed.
Parts are easily available.

 

If armature and brushes are good and stater reads open then get another and a good wiring diagram. remove all acessory loads and start up. Read charge voltage at the battery (about 14 vdc) If its low and getting lower then shut down and start looking for bad wires or connections. If it does ok with accesorys off ( lites,radio etc) start connecting stuff back one at a time and keep an Eye on the voltage. If one particular thing drags the voltage down then that's the culprit or it's wires.
Loose connections can cause overloads too. Make sure all your connections are good. Hopefully it isn't something in the starter ckt draining off power. Protect that new stator by allowing it to cool each time your check something out. If it's a connection you might find it by feeling around on the harness for a warm spot. Just have to thrash it out.

 

I just remembered- -
One of my electrical gremlins when I bought my 750- the electrical connector for the 3 white wires from the alternator had melted, and 2 of the three were in contact, cancelling themselves out I guess. My bike was getting power from just one white wire. With all that abuse it didn't fry the alternator or the voltage regulator!

 

Here's what I found so far,

The brushes measure out to 8.34mm from the wear limit line to the tip.

But, there was a little oil in the bottom of the housing. Not enough that it could weep out of the drain hole, but there was a little oil on the brushes, and on the rotor face.

The o-ring for the shaft housing might be leaking, so I gonna replace that, and get some new brushes here locally, if I can. The shaft seal was dry, so oil was leaking there.

I'll then clean off all the oil residue on the rotor/stator and put her back together and see what I have.

I'll report back my results.

Thanks,

 

Well, got the oil seal replaced, cleaned out the cavity of all oil, cleaned the brushes, rotor and stator, and was pulling 14.75 volts at the battery.

SWMBO rode it for a few days, told me that the trun signal stopped flashing, and looked "dim."

Sure enough, with the bike hot, the rotor ohms out at 0.5 ohms and the stator ohms out at 5.2 ohms. Those are out of spec when hot. When the bike cools, the numbers get closer to spec, but not at or under.

So, now that I have the oil problem fixed, I guess the next step is to replace the rotor and stator, and maybe the brushes.

Chacal, here I come with a credit card #!

 

Try cleaning the wire-end terminals with sandpaper, a tiny file, etc. and re-measure.

Did you test the rotor AT THE ROTOR (on the copper strips) or at the terminal connection?

 

On the actual rotor.

I just took another reading, now that the bike has cooled.

At the rotor, I have 4.5 ohms.

At the stator white wires, I have .5 - .6 ohms.

The brushes measure 8.34mm from the tip to the wear line.

The terminals are clean, and I applied dielectric grease on all connections. There is no corrosion, nor are they melted.

 

So, I got the parts I orderd from Chacal, and the parts are fantastic. Better than new!

But, I am still having problems... See below:

I got the parts installed and am still getting 11.78 VDC. At about 3500RPM, I barely make 12 VDC.

Since I replaced the connector for the voltage regulator, with a watertight one I got from an auto salvage yard, I can't really test the "V1, V2" scenario, but I ohmed out all the diodes on the rectifier and they are all good.

Also, kinda weird, if I measure the resistance of the rotor, at the rotor face, I get the 4.5 ohms. Cool. And if I measure the resistance from the brush, to the connector, I get 0.2 ohms. Cool. But when I measure the resistance with it all assembled, the rotor measures 13.2 ohms, at the connector end of the brushes wire.

Also, the stator consistently measure 0.2 ohms between any pole. So I know they are rock solid too.

Can it be the voltage regulator?

 

Could be the Reg/rect unit, or... double check your ground connections...
A loose ground can suck voltlage away as well....

 

It could be the regulator.
Make sure you DON'T get a circuit between any of the 3 white wires and ground, or between the brown/green field wires and ground (Make sure you test with the ignition off.).

Try to test these at the regulator.

Also, check the red wire from the regulator is connected to the battery and black to ground.

Finally, see if there is 12volts on the brown wire at the regulator when the ignition is switched to on.

A member has posted a load of XJ wiring diagrams (Type "Thunder" in search and it will come up).

Follow the drawing closely and you should be able to see how the charging system works.

The white wires fom the alternator feed AC voltage into a full wave rectifier (Six diodes), this gives. DC.
The regulator controls the current flowing through the rotor and brushes, on the green wire, to charge the battery. the 12v comes from the ignition on the brown wire.

Hope this helps?

 

While I had it apart, I noticed a little oil drip from the oil nozzle that is just behind the rotor, and to the left. It sprays oil up on the rotor shaft/chain region.

I then noticed that the roll pin, was missing and that the oil nozzle was not aimed the correct way! So, very little, if any oil was making it through that oil nozzle, and if any made it through, it was NOT spraying that region, it was spraying the opposite way!

I pulled the nozzle, replaced the o-ring and discovered that the PO had broken off the roll pin, inside the nozzle. OMG!!

I spent the better part of 6 hours, and about 5 drill bits, drilling out the broken part of the roll pin.

Finally got the remnants of the roll pin material out, and inserted a new roll pin, with the new o-ring and replaced the nozzle, aimed in the right direction!

So, even though I haven't resolved the charging issue yet, I fixed another problem, left behind by the PO.

I feel so bad for Rosie, and all she has been through!

 

If it makes you feel better, my bike has had a series of PO's who bodged things up (Not sure if this word is used in the US?). Including fitting the WRONG regulator so the battery was overcharging all the time!

As fast as I fixed things, something else went wrong.

 

Bodged is fine! LOL. I hear you!

I think I have most of the POs "bodgeries" sorted.

Now I just want to get her finished so SWMBO can ride!

Thanks for the kind words.

 

Try disconnecting the rotor wires from the rectifier and apply 12 volts to them and then check AC volts from the stator.

 

Re: Charging system keeps failing *** UPDATE ***

UPDATE

I got a voltage regulator regulator/rectifier from Chacal, along with connectors, wire spades and clips.

Got it all together and took Rosie out. I have a voltage meter attached to the battery terminals, and have it by the seat, so I could monitor the voltage at different speeds.

When I first started her up, I was getting 14.75VDC at choke idle. As it warmed up, the voltage dropped, not surprising.

At warm idle it was dancing around 12.10VDC But as I twisted the throttle, and got past 1800RPMS, the voltage climbed to 13.75VDC

Rode her for about 20 minutes, checking the voltages at different times and it was behaving like I would expect. It drops down to 12.10 or so at idle, and picks right back up when I take off.

OK, so the first ride out, everything works. So what. What happens the next day, or day three? In the past, the battery voltage, while off, was at 11.78VDC. So the new charging system was not charging.

But, after I replace the reg/rec and connector, the system is spot on! SWMBO and I went out on Saturday, and did 125 miles. IF it was gonna be FUBAR-ed, now is the time. Well, the battery is at 12.78VDC while off.

The final test is when my son takes Rosie out and calls me about an hour later to come get him and Rosie. "I don't know, Dad, she's just dead?"

Well, after about 5 hours, I texted the boy and he texted be back that "Rosie is kicking serious a$$!" I think to myself, did I finally fix her?

A couple of days went by, and I would check the voltage, just to see where the battey is, and it is parked at 12.78VDC.

The boy takes it out again, and returns several hours later. "No problems, Dad, she still kickin' serious a$$!"

Chacal get's all the credit for the fix. His parts, top quality parts, made the difference. I bought a used reg/reg from him and it is spot on! I am so freakin' happy! And so is SWMBO!

Thanks, Chacal!