DC Voltage Drops While Running

[veloduke]

I'm missing it. Where are the yellow wires connected to ground (other than the generator is grounded inside, and the rectifier is grounded)? The pics show they are connected to the rectifier.

Yes, that is what I am referring to, the wiring inside the alternator:-

Alternator.jpg

Two wires coming out, joined at the centre to ground.

The problem with old bikes is that you don't know what a previous owner may have done, e.g. changed the alternator.

Wiring.jpg

This how it would have been wired with the Duc reg/rec.

Without having the bike in front of me I can't be 100% sure, but it makes sense to me to remove the ground and run it as a true 2 wire alternator. It should then work with the Electrex reg/rec.

With the centre grounded, there is another path for the current to flow.

[mrkprsn]

How do I individually test each of the yellow AC wires? Positive multimeter lead to one yellow and negative lead to a ground? Or do I just reverse the multimeter leads to the opposite yellow wires? To test voltage so far I connected one multimeter lead to each yellow wire with the bike running off the battery and got 24V-42V depending on RPM.

- Connect all the wires (generator/rectifier/battery/switches) up like normal. Disconnect the generator wires from the rectifier. Connect your multi meter pos lead to one of the generator wires and the neg to where that wire connects to the regulator. Test for volts. Then switch the wires on your multimeter and test for amps. Do the same thing for the other wire. Connect the generator wires back to the rectifier and test for voltage at the battery. After doing these tests, you will know if your generator is healthy. Please post those results.

There IS continuity between the yellow wires, and there IS also continuity between each wire and ground, which I understand is by design:

- That shows that the ground is still in place and hasn't been altered. I don't know if modern rectifiers can be used with the generator grounded or not. It appears the generator would put out more amps which would help you. I don't know if that would effect the voltage though.

- Did you do the Ohms/Continuity tests on the rectifiers. Somewhere in Motoscrubs.com ("test rectifier") there is a list of what to test. I would do this on the original one and the modern ones. I just went through two rectifiers (one original and one modern). My testing confirmed they were bad. Run the same tests on the modern ones. I would do this before going through the effort of disconnecting the generator ground. Please post the results.

[blaat!]

Sorry for the delay. Summer vacations is over now. Back to work!

- Connect all the wires (generator/rectifier/battery/switches) up like normal. Disconnect the generator wires from the rectifier. Connect your multi meter pos lead to one of the generator wires and the neg to where that wire connects to the regulator. Test for volts. Then switch the wires on your multimeter and test for amps. Do the same thing for the other wire. Connect the generator wires back to the rectifier and test for voltage at the battery. After doing these tests, you will know if your generator is healthy. Please post those results.

When putting the multimeter inline with one yellow wire I get 6.5V AC and I get 6A plus with the ammeter inline.

When putting the multimeter inline with the other yellow wire I get 7.0V AC and I also get 6A plus with the ammeter inline on this wire.

With the regulator disconnected and one multimeter lead hooked up to each yellow wire coming from the stator I get 24V-42V depending on the RPMs.

With everything hooked back up and running I get 6.1V at the battery. If I shut the key off the battery reads 6.4V, which is the actual charge of the battery.

Below are the results I get when bench testing the stock regulator

126.jpg

So I went ahead and disconnected the stator ground as Max suggested and tried the Electrex World regulator:

InkedIMG_6167.jpg

Shrink wrapped and zip tied it in place so it won't vibrate and break, and the modification could be undone:

IMG_6170.jpg

With the bike running off the battery and only the stator and regulator connected to each other (and isolated from the rest of the bike wiring) I still only get 5.0V coming from the DC side of the Electrex World regulator.

I checked the Hz now with the stator ground disconnected and it is 150-200 depending on RPMs

I'm totally stumped again

[mrkprsn]

I am a little confused. You said you tested the generator wires and got 6.5-7v and 6a. Then you said you disconnected the regulator and got 24-42v. How did you do the inline test without disconnecting the generator wires?

Try this: Only disconnect one wire from the regulator and do the voltage and amp inline test while the bike is running. Then plug that wire back into the regulator and do the same thing with the other wire. What are those results?

It may be the regulator since it did not check out but I would like to make sure the generator is working correctly.

[Bevel bob]

As stated above you have to un-ground the stator and join those connections together if you are using a modern rectifier box. My 67 Mark 3 has been using this method for many years . I also disconnect my battery when the bike is not in use . Charge stays up much longer. Bike is wired so all charging system is seperate from old wiring and avoids headlight area.

[veloduke]

With the bike running off the battery and only the stator and regulator connected to each other (and isolated from the rest of the bike wiring) I still only get 5.0V coming from the DC side of the Electrex World regulator.

According to the Electrex instructions, you need a battery connected to the regulator:-

Screenshot 2023-09-12 080104.jpg

[blaat!]

Try this: Only disconnect one wire from the regulator and do the voltage and amp inline test while the bike is running. Then plug that wire back into the regulator and do the same thing with the other wire. What are those results?

This is exactly what I did. One side shows 6.5V AC and the other shows 7.0V AC

When I test across the stator wires (nothing connected to the regulator) I get 24V-42V AC

Good catch Max. You don't miss a detail I can try running it with just the stator, Electrex regulator, and battery connected, but isolated from the rest of the electrical system on the bike. I'll run the bike off my DC power supply to spin the flywheel.

The brand new fully charged battery reads 6.39V

If that number goes up, it's working. If that number goes down, I'll probably need to start thinking about getting the stator rebuilt/re-magnetized or moving to a 12V system

[mrkprsn]

When I test across the stator wires (nothing connected to the regulator) I get 24V-42V AC

Can you explain how you did this test? I don't know what you mean when you say you tested across the stator wires? How do you test for volts across the two AC wires?

[blaat!]

Can you explain how you did this test? I don't know what you mean when you say you tested across the stator wires? How do you test for volts across the two AC wires?

I disconnected the two yellow stator wires from the regulator with the bike running. I set the multimeter to measure AC current and connected the red lead to one of the yellow wires coming from the stator, and connected the black lead from the multimeter to the other yellow wire coming from the stator.
That is how I understand this Ducati Bulletin:

stator check.JPG

[blaat!]

So I think progress has been made!?!

I connected the two Electrex World regulator yellow wires to the stator, and then I connected the red and green wires from the regulator to the battery only. These three components are hooked to each other and completely isolated from the rest of the electrical system on the bike. Then I hooked the bike up to a DC power supply so that it would start as normal.

With the bike off the battery voltage read 6.40V
When I started the bike the voltage at the battery climbed to 6.86V

Unfortunately when I connect the rest of the electrical system the DC voltage at the battery still drops from 6.40V to below 5.90V while running.

I now suspect two problems. One was the internal stator ground isn't compatible with the Electrex World regulator. That is resolved (thanks Max!)

There must be another problem somewhere in the bike's electrical system that is drawing extra amps?

I also just stumbled across this:

charge mod.JPG

I think that might have been done on my bike but I changed it back because it didn't match the wiring diagram. I didn't notice any difference. Anyone know the thinking behind this change? Maybe this could solve it?