[Mustangs6551]

Just replaced the regulator/rectifier on my 95 (single phase) 916. I'm still not getting a charge, just the 12.5 the battery puts out. Battery is 6 months old and lived on a tender it's whole life. I've tested all the wires and there is continuity where there should be. Between the two yellow wires coming out of the case where the stator is I get .6ohms resistance. Manual calls for .2 to .4 that's the only squirrelly thing. There is no grounding from either for the yellow wires.
One spot I'm less sure about is the 30a fuse listed on the wiring diagram. I found a fuse that is mounted next to the battery, I'm not sure if that is it but that fuse was good. Also good was the 3a fuse in the fuse box.
Any ideas?

 

[Mustangs6551]

Just ran an unregulated voltage test by disconnecting the two yellow wires. I got about 20v short at each of the specified positions. 20vs at idle (calls for 35), 50v at 3000 rpm (calls for 70). Bad stator.

 

[Namor]

Maybe, pull the cover and have a look.

 

[belter]

this outlines how to do a loaded test using a 12v rectifier. that's the best test for the stator.

https://bradthebikeboy.blogspot.com/2012/11/charging-system-diagnosis-procedure.html

the 30a next to the battery is the maxi fuse which is the circuit between the reg and battery.

 

[916duc]

The manual does not specify, yet the output of the two yellow wires are to be disconnected from the voltage regulator and measured in AC volts. The output at 4000 rpm is normally 55-60 ACV. There are many ratings listed throughout the original manuals that are incorrect, especially in the earlier years.

My own 95-915 had a hack mechanic butcher the installation of the side cover causing the need to learn testing of the 2 phase charging system.

 

[belter]

if you're seeing 50v ac with rpm i'd call that a pass. the loaded test with a rectifier is much more conclusive though. i have seen stators pass the ac test, but fail a loaded test.

 

[Mustangs6551]

Belter thanks, I'm leaning toward shaving a second bad rectifier. You'd think it would put out something if the stator is generating anything. Earlier I tested the red and black wires that lead out of the regulator with them disconnected. Still zero volts there. I can't imagine I hooked up the regulator wrong, I assume as long as the two yellow wires are connected it should give something if the regulator is functional.

 

[belter]

my advice is to follow the steps in order. it may be a reg, but it's pretty easy to get caught out, and the lack of diagnosis done before people start replacing parts drives me nuts.

 

[bigbadbass2]

Mustang, if it comes down to stator visual inspection, take the time to rewire the pathetic, tiny gauge output wires with larger. I used 12 gauge as opposed to laughable OEM yellow (16 gau?) pictured, wired direct to RR input connector, eliminating any mid connector.

What RR are you using? If needed, an affordable, genuine Shindengen Mosfet replacement is advisable. Beware junk copies. In reliable service 10 years now...no issues.

Add a voltmeter of your choosing...good luck with it.

 

[Strega]

I'll pass on my observations and experience with my own 916 charging system failures.

The stator windings and leads are just lengths of insulated wire. If the insulation fails, the wires short together and the alternating current output of the stator is diminished - often to zero. The voltage differential between stator wires increases as engine rpm increases, so shorting due to damaged insulation is more likely as voltage increases.

The stator wires carry a substantial current, so any point of electrical resistance is a point of heat generation. The connector between the regulator/rectifier (RR) and the stator is THE point of increasing resistance over time due to corrosion — and because it has a higher resistance than the attached wires. Consequently, the connector gets hot — really hot — and because copper wire is a good conductor of heat, the adjacent wires get hot for a substantial distance from the connector. Immediately adjacent to the connector the insulation becomes discolored from internal heat, but more importantly, it looses the ability to insulate its wire from adjacent wires and components.

On Ducatis, the stator wires are run inside a sheath that provides additional insulation from adjacent grounded components, but this causes a problem — inside the insulating sheath, the stator wires are held close together so they touch.

So what happens is — the connector heats the stator wires, the hot wires damage their insulation, the wires short together where they touch inside the sheath (at higher voltages produced at higher engine rpm).

You can diagnose damage to the insulation to the stator winding by doing a continuity and resistance check using a low-voltage ohmmeter because the windings have a different type of insulation than the lead wires. A diagnosis of damaged and shorting lead wires will display normal battery charging voltages on an on-board voltmeter, but at higher rpm the voltmeter will drop to sub-12 volt values indicating that you’re not charging.

When the stator output is shorted out it can damage the internal electrical components of the RR. Often, a new RR will fail soon after replacement because the damaged wiring was replaced only where it showed discoloring adjacent to the connector.

On my 916 I had four RR failures before replacing the stator lead wires. The insulation on the stator wires where it entered the engines side cover was so soft from heat that I could peal it back with my fingernail. Removing the inline connector and soldering the wires directly solved the problem with over heating.

Finally, you should also be aware that an RR will often fail from overheating because it is located inside a fairing and adjacent to exhaust pipe heat. A hot environment combined with internal heat generated by the RR is a well known problem. Relocating the RR to a location on the bike where it can receive better cooling air flow is a wise modification.

 

[Mustangs6551]

Ok folks, I think I've solved it. The regulator I bought was from electrosport: https://www.electrosport.com/products/esr515-regulator-rectifier-ducati-1-phase-charge-light-output It's aftermarket and came recommended from a friend. Turns out the issue is grounding. The electrosport RR has a black wire that looks like a ground (Haynes manual also implied it's a ground). Turns out it's actually a dummy wire they only put in so that people don't freak out. Modern RRs don't need this wire, in the past it did some voltage sensing.
Modern RRs uses it's own housing as ground. My bike is apparently missing a grounding strap (I've owned it 8 months and rebuilding it, the RR has never run). As it is, my RR is dangling isolated from any grounding, causing a problem.
Shout-out to electrosport for letting me talk to their very knowledgeable tech for about 30 minutes talking over the problem.

 

[SS904]

...where the stator is I get .6ohms resistance. Manual calls for .2 to .4 that's the only squirrelly thing.

Very minor point in the grand scheme of your problem, but you'll likely find that extra in your meter leads. Hold the leads together with your meter reading resistance. Pretty good bet you'll see that the leads are .2 ohms. Analog meters I used years ago enabled you to zero that resistance to compensate for the leads, but I've yet to see that on a newer digital meter. Maybe some expensive DVMs have a null feature, but my Fluke 87 or any average DVM I've come across does not.