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Discussion Starter · #1 ·
Before I install a new regulator/rectifier on my 1993 Ducati 900 Superlight, I ran a few quick tests on my alternator. The reading for the AC output across the 2 yellow wires was 30VAC @3,000 rpms & 40VAC @4,000 rpms. Can anyone tell me if this output is consistent with factory specs?

Thank you so much.
 

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sounds ok to me. i usually go a bit higher rpm wise, where you should see 70 or so.

if you get a little rectifier and hook that up you can test the loaded potential of the alternator, but it's not regulated so you don't hold it at 7,000 and send the battery to 25v sort of thing. you should see 16v with that test pretty quick (and then shut it down).
 

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Discussion Starter · #3 ·
sounds ok to me. i usually go a bit higher rpm wise, where you should see 70 or so.

if you get a little rectifier and hook that up you can test the loaded potential of the alternator, but it's not regulated so you don't hold it at 7,000 and send the battery to 25v sort of thing. you should see 16v with that test pretty quick (and then shut it down).
Well, I don't know if it's relevant, but the reason that I am replacing the reg./rec. is because the voltage at the battery was 16VDC @ 4,000 rpms (as well as a partially melted headlight connector). So that seems to tell me that the alternator is cranking out adequate voltage. Does that make sense?
 

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was it an original ducati or "correct" replacement reg, they have a voltage reference from the battery that goes through the loom and if it is low due to age and all that crap it will give a misleadingly low voltage at the reg and so the reg puts out enough voltage to make that reference what it wants.

it's not a reg issue if that is the case. fitting a reg without the reference wire does bypass it though, like the later fitment sh579b.

from my charging system write up:

If you use an original style or Electrex or other single phase regulator that uses a reference voltage input (the two wire flat connector has one wire to run the light, the other is a reference) then you need to make sure the reference is accurate. This reference is switched through the ignition switch and runs through the loom. If the reference is low, due to the resistance that naturally builds up in an old loom, the regulator will think the battery voltage is lower than it actually is and it will overcharge the battery. I think it’s the white/red wire (or maybe pink?).

You can either check the voltage in this wire or (better) run a jump wire from the battery positive to the connector. I pull the connector apart enough that it’s still connected, but you can touch the terminal. Then, with the engine running and while checking the battery voltage, touch the jump wire to the terminal. If the battery voltage drops instantly (and it will if it’s overcharging) the easiest fix is to cut the reference wire on the loom side of the two wire flat connector, fit a relay running battery power direct to this wire into the regulator and switch the relay on with the loom side of the reference wire coming from the ignition switch. 906 Paso have done this for years, and I’ve seen a few Monsters and SS do it.

The SH579 3 phase regulator doesn’t use a reference, so fitting one does away with this potential issue.
 

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Not a good image but it is from my 1993 superlight manual. I would ditch the Ducati electronica rectifier and only run one if you are trying to keep this rare bike 100% original. I think I would adapt a later rectifier and keep a good Ducati electronica in a box for the next owner.
 

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Discussion Starter · #6 ·
The faulty reg/rec is a Electrex unit. By "reference" wire are you referring to the "no charge" indicator light?
 

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Discussion Starter · #7 ·
Not a good image but it is from my 1993 superlight manual. I would ditch the Ducati electronica rectifier and only run one if you are trying to keep this rare bike 100% original. I think I would adapt a later rectifier and keep a good Ducati electronica in a box for the next owner.
Thank you. If these specs are correct, then the VAC I am getting is quite low. Is this indicative of a faulty stator?
 

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there are two wires that go into the loom - one is the charge light, the other the reference voltage.

if it was knocking out 16 i'm guessing the alt is ok.
 

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Discussion Starter · #10 ·
there are two wires that go into the loom - one is the charge light, the other the reference voltage.
Forgive me if I'm a bit dense when it comes to electrical issues. If there is considerable resistance in the reference wire (which leads to overcharging), shouldn't I be able to disconnect the reference wire & then check the battery voltage? If the indicated battery voltage is now within specs, that would seem to suggest that the reference wire was indeed the culprit. Does that make sense?

Thanks.
 

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Manuals are notorious for bad information, in this case I agree with Belter and the end results is that you are producing Too much power not too little so look away from the stator and look to your regulator. This is the component that controls the power created by the stator so if you are producing too much this is the likely culprit.

Electrex as a brand has been less reliable in my experience than the oem Ducati electronica units that are known for failures, I would consider not using one if it was given to me for free. based on MY Experience I have had better luck with a Ricks https://ricksmotorsportelectrics.com/l/rectifier-regulators

But my favorite is the oem Hitachi that was sold as a replacement back in the 90's. These days everyone is on the MOSFET bandwagon so there is that option as well but short term success is not long term data so I will wait to jump on that bandwagon. Every rectifier I have had on my personal bikes that is a later oem style has been 100%, I have changed out a handful in the last 10 years on customers bikes (less than 5).

Betler may be on to something if the rectifier you have is looking for a reference voltage and getting bad info, best to start there and if you find the rectifier is bad but a quality replacement rather than what you have now. I have bought rectifiers of the right (oem) type for years for under $100 and no failures, I would choose that over a inexpensive poorly made version anyday. Know that some/most rectifiers will not use the voltage sensing wire or keep a functioning charge light. In my experience neither is a issue as most rectifiers will last better and you will not need a charge light. The Ricks model did retain a charge light if you care.
 

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Discussion Starter · #12 ·
Thank you, ducvet. In fact, I ordered a MOSFET regulator from Rick's since I felt that the regulator was the problem. However, I was unaware of the reference wire being a potential issue. In my response to Belter above, would disconnecting the reference wire at the connector & then checking the voltage at the battery determine whether the reference wire is the culprit? In other words, with the reference wire disconnected, if the battery voltage at 3,000 rpms is within specs, would that suggest that the reference wire was an issue?
 

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If you simply run a jumper wire in the same path as the reverence wire to know it is getting correct voltage you can tell if it changes the voltage or not. I do not think it will be worth the time as your new rectifier will likely not use a voltage wire, and will solve the problem anyway.
 

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Electrex as a brand has been less reliable in my experience than the oem Ducati electronica units that are known for failures, I would consider not using one if it was given to me for free. based on MY Experience I have had better luck with a Ricks https://ricksmotorsportelectrics.com/l/rectifier-regulators

These days everyone is on the MOSFET bandwagon so there is that option as well but short term success is not long term data so I will wait to jump on that bandwagon. Every rectifier I have had on my personal bikes that is a later oem style has been 100%, I have changed out a handful in the last 10 years on customers bikes (less than 5).
As always, Ducvet has good insight. Let me chime in here as well.

In my experience as well, Electrex has not been a great product. I'd avoid them if at all possible.
Rick's has been solid and reliable for years, and their new MOSFET based products are nice. We have been testing them for a few months, and the performance is really good. But, as DV points out, this short period of time is not really adequate to predicting long term success.

The one area where I will disagree with DV regards the MOSFET regulators, specifically the OEM versions made by Shindengen.
In short, these have now been in use for more than a decade, and I have seen so few failures that I can counts them on one hand. There is no question that these is the single biggest jump in charging system reliability in the last 25 years.
I have helped people with every possible type and style of bike change over to the FH020AA- hundreds- perhaps thousands of times- with good results every single time. Again, this has been the case for me personally for the last 10 years.
I cant imagine a more reliable product.
 

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As always, Ducvet has good insight. Let me chime in here as well.

In my experience as well, Electrex has not been a great product. I'd avoid them if at all possible.
Rick's has been solid and reliable for years, and their new MOSFET based products are nice. We have been testing them for a few months, and the performance is really good. But, as DV points out, this short period of time is not really adequate to predicting long term success.

The one area where I will disagree with DV regards the MOSFET regulators, specifically the OEM versions made by Shindengen.
In short, these have now been in use for more than a decade, and I have seen so few failures that I can counts them on one hand. There is no question that these is the single biggest jump in charging system reliability in the last 25 years.
I have helped people with every possible type and style of bike change over to the FH020AA- hundreds- perhaps thousands of times- with good results every single time. Again, this has been the case for me personally for the last 10 years.
I cant imagine a more reliable product
.
In 2009 I purchased a couple used FH010 (Kaw 1000) off Ebay around $50 each...long prior to release of the current standard FH020. Using this basic wiring photo, and recommended Furakawa weatherproof connectors, I doped one on both my '95 900SS and my '98 VFR800, also wiring voltmeters on each. 10 years later, both STILL intact and fully operational on both bikes. SUPER reliable. Beware the cheapo copies on Ebay...must be original Shindengen.
 

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the only issue i have with them is the packaging, and in particular those great big connectors. make it hard to fit things in sometimes. i did a 999 a couple of weeks ago and ended up mounting it off the belt cover screws on the rh side.
 

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Those connectors are much more reliable than the inline style of years ago.

It may be a bit of work to integrate the newer parts on an older design, but it is well worth the trade-off.

This is the 999 I did a few years ago when the SH847 first arrived. I had started relocating them to the right side when I built my 1098 with the big radiators maybe back in 2010ish? It's a much better location, IMO, and requires a minimum amount of work.
 

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