Here We Go Again....charging issues G5

[Dan Beaman]

Kiwi Roy's tag line is perfect!!!

Moto Guzzi - making electricians out of riders since 1921

I've been redoing my entire charging system on my '81 G5, replacing every wire end, replacing the rectifier, regulator and a used entire alternator. Still not charging fully. I found the used rotor was bad, but had another. It tests 3.4 ohms across the contacts so I'm satisfied. With the new regulator in, I have no idiot light on the dash for the alternator and I'm only testing 12.1 volts at the battery with engine running at 2,000 rpm. I out the old back in and the light functions, but the battery tests 11.9 volts. It should be 14.5.

Bad regulator? Rectifier? Something else? I'm really figuring regulator and I may have damaged it while redoing all this wiring.

[Tom]

Your dash light needs to be working to "excite" the charging system.  No light.  No charge.

[brider]

Your dash light needs to be working to "excite" the charging system.  No light.  No charge.

Yep, LITERALLY just went thru this on my Cal 2, which has the exact same system as your G5 (I think).

Simple circuit from the rectifier DF rectifier D+ post to the BATT bulb, it turned out my BULB WAS BAD, last thing I'd suspect, but it was.

[Dan Beaman]

Your dash light needs to be working to "excite" the charging system.  No light.  No charge.

Then how was it on with one regulator and not the other? How does this correlate?

I have more bulbs so an easy test!!

[injundave]

Do yourself a favour and check out one of these. Best bucks I ever spent on my T3.

 https://www.euromotoelectrics.com/product-p/edl450-altkit105.htm

[Dan Beaman]

 I love that idea but more $ than I have any business doing right now!!

[Tom]

Then how was it on with one regulator and not the other? How does this correlate?

I have more bulbs so an easy test!!

Did it stop working with the new regulator?  The bulb would be the weak link.    For some reason, I'm thinking that you'd need to flash the rotor.  Someone can tell me if I'm wrong.

[Dan Beaman]

Ok....you all had me going so I just went back to my shed. With the new regulator in, the bulb is out. When I put the old one back in, the light is on! Not a bad bulb.

The new one gives me more voltage but not enough. So we've eliminated the bulb issue.

I'm leaning to something fried in my new regulator. 

Thoughts???

[Dan Beaman]

Did it stop working with the new regulator?  The bulb would be the weak link.

Yes that's exactly what happens!! The bulb is ONLY out with the new regulator.

[Chuck in Indiana]

I've never heard of this one.. It's probably KR time. 

[Groover]

I'd quadruple check the wiring. Sit back, take a look, take a break, take another look, repeat.

Here is a chart that may help. It's very simplified and doesn't show things such as grounds and bypasses all harness connectors and such, but it should help clarify I hope.

[brider]

I'd quadruple check the wiring. Sit back, take a look, take a break, take another look, repeat.

Here is a chart that may help. It's very simplified and doesn't show things such as grounds and bypasses all harness connectors and such, but it should help clarify I hope.

Groover, as helpful as I found your diagram in the past, it is in conflict at the 61 and D+ post versus Bender's website:

http://www.thisoldtractor.com/moto_guzzi_tonti_wiring_harness_install_rectifier_-diode_board-_connections.html

[Groover]

Groover, as helpful as I found your diagram in the past, it is in conflict at the 61 and D+ post versus Bender's website:

http://www.thisoldtractor.com/moto_guzzi_tonti_wiring_harness_install_rectifier_-diode_board-_connections.html

Thanks right, you did mention that to me once before. I need to dig into this again to confirm.

[Groover]

Maybe those two terminals are interchangeable, not sure. I wish I could remember whom gave me this hand sketch I'm posting now when I first started messing around with my G5 in 2014. It was someone from here, but I was new here and don't remember whom sent it to me and I can't find any emails or PM, so it may have been text... anyway, based on this granular diagram, it appears those two spades could be merged or swapped??





Hopefully something (Kiwi Roy  ) can chime in to clarify.

[Dan Beaman]

Your diagram was very helpful. I had 2 wires on the alternator in the wrong places, the black and the blue. The rectifier I had correct. Now I still have no charge....11.9 volts at 2,000 rpm. Now it’s the same no matter if it’s old or new regulator and the idiot line is on with both so not a bulb problem. Rotor still tests at 3.9 ohms or there abouts. So stator is good, rotor is good, wires are good. In my mind that leaves either the regulator or the rectifier As bad

[Chuck in Indiana]

Ok, now we're getting somewhere. Pull the three yellow wires off the alternator, start it up, and check voltage directly out of the alternator. It should be close to 40 volts AC between the three posts. 1-2, 1-3. 2-3. They should be very nearly the same. If they are, *then* you can say the stator, rotor, brushes, etc. are ok and look elsewhere.

[Groover]

And then after you do that, then try flip-flopping the D+ and the 61 from the rectifier as brider pointed out.

I think if you had a bad regulator, the voltage would fluctuate a lot with changes in throttle (hence regulating). So maybe the diode board, be sure it's grounded properly.

[Kiwi_Roy]

Ok....you all had me going so I just went back to my shed. With the new regulator in, the bulb is out. When I put the old one back in, the light is on! Not a bad bulb.

The new one gives me more voltage but not enough. So we've eliminated the bulb issue.

I'm leaning to something fried in my new regulator. 

Thoughts???

You don't say if the motor is spinning when the light is out.
It must light with the key on but not spinning the current from the lamp is running through the rotor, if its off its not conducting from D+ to DF and therefore not getting excited.
If the light is out with the motor idling that's ok
Terminal D- must be grounded to turn the regulator On. Brider's diagram shows battery negative on D-, the negative is grounded by the main ground and it's also grounded by the brush in the alternator.
The light should go out with the motor spinning because the 3 small diodes connected to terminal D+/61 drive the Voltage up until there is no difference in Voltage across the lamp.
The rectifier terminals 61 and D+ are connected together.
D+/61 cannot go higher than the battery Voltage because the large main diodes have the same Voltage bias as the 3 small diodes.

This California II schematic shows the Bosch system quite clearly.
http://www.thisoldtractor.com/guzzi007/schematics/1981_California_II.gif

[Kiwi_Roy]

Maybe those two terminals are interchangeable, not sure. I wish I could remember whom gave me this hand sketch I'm posting now when I first started messing around with my G5 in 2014. It was someone from here, but I was new here and don't remember whom sent it to me and I can't find any emails or PM, so it may have been text... anyway, based on this granular diagram, it appears those two spades could be merged or swapped??





Hopefully something (Kiwi Roy  ) can chime in to clarify.

That looks like some of my chicken scratching

If you combine it with the drawing Groover provided you get the whole picture.


When you turn the key On (motor not running) the current from the charge light travels to 61 then from D+ to the regulator D+, through the transistors and out the DF terminal to the slipring brush of the alternator, through the rotor and to the grounded brush and back to the battery Negative,
So if you have an ammeter you can measure that current by pulling a wire off and inserting your meter in series. You can also measure the Voltage at the alternator field DF, I forget what it is but I'm guessing less than half a Volt. You will get a Voltage also at either of the D+ terminals. it will be a bit higher i'm guessing 0.5 to 1 Volt.

This initial current provides a weak field for the alternator, as it starts spinning this induces a weak AC current into the stator windings. U, V & W
From U, V W the three small diodes rectify the AC and push the Voltage at 61/D+ Positive which provides more current to the regulator and rotor field until soon the Voltage is so high on 61/D+ it's higher than the 12 Volts going into the charge lamp so it goes out.
At the same time the Voltage on the Positive rail of the main rectifier is higher than the battery so it charges the battery.

If you look at the diodes between UVW & 61/D+ it's the same arrangement as between UVW & the Positive rail, so since the diodes all drop around the same forward Voltage it stands to reason 61/D+ is the same Voltage as the Positive rail which is connected to battery Positive, that's how the regulator knows when to cut back on the excitation Voltage to the rotor, the transistors cut back on the current they pass.

[Dan Beaman]

So Roy, I've not done all that testing yet, but I have exactly zero volts coming out of the 3 yellows on the alternator with all running. The rectifier wires are all correctly placed. I pulled the covers and battery out to check that. The stator shows no open circuits and the rotor tests 3.4 ohms. Is there a test just for the rectifier? I'm beginning to think that between the front and back of the bike, I just plain have an open circuit from a bad wire someplace.

[Groover]

When I was losing my mind like this, I literally made test wires to bypass everything, then started working my way back. Using the color chart posted above, you can easily accomplish that with any wires you have laying around. Doing that, you eliminate harnesses throughout the bike and other craziness(es) that happen under the dash to get to the little bulb. Other than that, the 0 volts you get where Chuck in Indiana says those should read 40v, then maybe there is an issue with the alternator? Don't know, my advice is that; Just get some spade connectors at radio shack or walmart, and make some temporary wire connections to the main components.

[Groover]

That looks like some of my chicken scratching

Ah, who else would it have been! Thanks again for that, it really helped me understand a lot at the time. Sorry I couldn't remember whom sent it, but now I won't forget!

[Kiwi_Roy]

So Roy, I've not done all that testing yet, but I have exactly zero volts coming out of the 3 yellows on the alternator with all running. The rectifier wires are all correctly placed. I pulled the covers and battery out to check that. The stator shows no open circuits and the rotor tests 3.4 ohms. Is there a test just for the rectifier? I'm beginning to think that between the front and back of the bike, I just plain have an open circuit from a bad wire someplace.

It seems to be the new regulator you are having trouble with the charge light current should go through that and out to the rotor take a measurement of the current or Voltage. If you have no current through the rotor the 3 yellow wires won't have any Voltage on them.

[Dan Beaman]

So how both at the D+  and 61 connections on the rectifier,  there are  in the vicinity of11.4 volts. I checked continuity on the Y wire from the rectifier to the alternator. Good. There are only .1 volts there with the switch on. With the regulator plugged in, there are 10.5 volts to the DF plug on the alternator. That appears to me to leave only the ground side of the brushes/alternator as a potential issue.

[Kiwi_Roy]

10.5 is too high on DF when the motor is not spinning, tells me either the rotor is open or the negative brush is not grounded or not making contact with the slip-ring.

The charge light pull 1.2 Watts, that's just 100 milliamps (0.1 Amps)
0,1 Amps across 3.5 Ohms = 0.34 Volts is all you should see at DF

With the key turned On and the negative probe of the meter grounded touch the positive probe on first one slip-ring then the other.
You should get a little Voltage on DF but zero on the other.

That Y connection is not really necessary it's not used on a classic 3 phase alternator.

[Dan Beaman]

I think, Roy,  you're verifying my suspicions with the ground....... It's really the only thing left. I'm going to follow Grover's advice and use a jump wire. 

[Kiwi_Roy]

I think, Roy,  you're verifying my suspicions with the ground....... It's really the only thing left. I'm going to follow Grover's advice and use a jump wire.

You can add an extra ground at the alternator and also one at the regulator
Don't forget the rectifier needs a good ground as well, all of the charge current has to get back to the alternator yellow wires right there, strap it to a motor bolt.

PM sent.

[Furbo]

Do yourself a favour and check out one of these. Best bucks I ever spent on my T3.

 https://www.euromotoelectrics.com/product-p/edl450-altkit105.htm

Sorry mate, but this is just grand advise. If you've not got $500 to spend on a 40yr old motorbike, you've no business owning it. sell it and buy an old Honda Dominator.

[Dan Beaman]

I'm now officially at a total loss. I jumped both grounds, the alternator and the regulator. No change. I tested continuity on all the rectifier wires, the stator and the rotor. You can read above everything else. Not charging.

[Groover]

Did you wire the little bulb properly?