Not another charging thread-No AC output

[Furious D]

I have been working on this for a few days and I am stumped. My 81 has no AC output
coming from the stator.

Checked the windings, All reading around .5 Ohms none showing a path to ground.

Ohmed the slip rings, 5.2 ohms ring to ring. Infinity to ground.

I have 12.46 volts at the brown wire to the brushes and a very slight magnetic field when I try the slap test. Brushes are well within spec as well. aLso disconnected the yellow wire , No change. This bike was charging fine when I bought it last year.


Any ideas?

 

[retiredgentleman]

I have been working on this for a few days and I am stumped. My 81 has no AC output
coming from the stator.

Checked the windings, All reading around .5 Ohms none showing a path to ground.

Ohmed the slip rings, 5.2 ohms ring to ring. Infinity to ground.

I have 12.46 volts at the brown wire to the brushes and a very slight magnetic field when I try the slap test. Brushes are well within spec as well. aLso disconnected the yellow wire , No change. This bike was charging fine when I bought it last year.


Any ideas?

This is from Curly's troubleshooting guide in our "Tech" section:

3. On the solid state regulator models all you need to do is locate the green wire at the regulator plug and make a jump from it to ground. That bypasses the regulator and allows full battery current to flow through the brushes out of the rotor through the green wire to ground. That causes the rotor to make a stronger magnetic field which in turn causes more current to flow in the stator. If your battery terminal charge voltage jumps up to 14.5VDC when you rev the engine then the regulator or the ground connection for the regulator is your problem.

 

[Furious D]

Yep ,tried the jumper trick on the green wire . It sounds like the motor drops in RPM's because it has a load on it but the voltage to the battery only rises about 4/10's of a volt and never rises above 12.75.

 

[pamcopete]

Furious,

12.75 is still above 12.5 so it seems that there is some output from the alternator. That scenario is typical of a shorted rectifier.

 

[Furious D]

I thought I had ruled out the rectifier being bad since it still does not have an AC output with the rectifier unplugged.



I am going to jump 12 V direct to the +brush and see what that does. If it still doesnt work I am going to guess the rotor or stator are bad even though they pass the Ohm test.


This is driving me nuts, I'm an electrician and work around big generators/AC motors all the time. Why cant I fix this tiny one?

 

[speez]

do you have a separate rectifire, reg? or is in 1 unit?

 

[pamcopete]

I thought I had ruled out the rectifier being bad since it still does not have an AC output with the rectifier unplugged.

FuriousD,

The '81 models have a combined regulator / rectifier on the same plug, so if you unplugged the rectifier you also unplugged the regulator so no current would go to the rotor and you would not get an AC output. You can check the diodes in the rectifier half of the reg / rect using an Ohmmeter between each white wire (yellow wire?) and the black and red wires. Should read resistance in one direction and close to infinite in the other.

 

[speez]

thats where i was going with that last post it wasn't adding up

 

[Furious D]

It has the combo rectifier/Regulator. I dont have the original 7 pin connector anymore, The connections looked a little flaky so I bypassed it with seperate bullet connectors till I decide what I path I will go. So when I was testing I just had the white stator wires disconnected only.

I decided to take a couple days off and will take a fresh look at it this week. Or I might just go out and shoot it with a 12 gauge.

 

[retiredgentleman]

At this stage maybe do a few more tests. Connect your VOM to read current flow into the rotor...............disconnect one of the brush wires to insert your meter leads. When you turn on the key you should read about 2 amps.

I use a 0.003" feeler gauge to test the magnetic field. Hold the gauge at 3/4" from the rotor nut. If the mag field is healthy, the gauge will pull over the 3/4".

If the rotor is working as shown by the above tests, then your stator is likely bad.............ground on the stator perhaps??

 

[Furious D]

Only reading about 5 mA thru the brushes.

I tried cleaning the rotor face today and jumpered 12V straight from the battery to the brushes as well, no change. It has a slight magnetic field when running but no where near what it should be.

I also retested the stator windings today with a megger,a meter that checks resistance to ground and found no problems. I guess it is time to pull the stator and rotor and see if I can find a problem. Damn this bike , I was hoping to have it on the road a couple months ago

 

[retiredgentleman]

Only reading about 5 mA thru the brushes.

I tried cleaning the rotor face today and jumpered 12V straight from the battery to the brushes as well, no change. It has a slight magnetic field when running but no where near what it should be.

I also retested the stator windings today with a megger,a meter that checks resistance to ground and found no problems. I guess it is time to pull the stator and rotor and see if I can find a problem. Damn this bike , I was hoping to have it on the road a couple months ago

The small magnetic field is just residual magnetism. If your rotor measures 5 ohms winding resistance, but you can only measure 5 ma current flow, then you must have a defective brush or the brush braided lead is open circuit. The brush needs to be 3/8" or greater in order to have enough pressure on the slip ring. Have a close look at the brushes/springs and leads, as they are a common wear item.

Meggering the stator was a good check to do.