Diagnosing Alternator - 2010 848 - Ducati.ms - The Ultimate Ducati Forum
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post #1 of 77 (permalink) Old Dec 17th, 2015, 5:28 pm Thread Starter
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Diagnosing Alternator - 2010 848

G'day all!

My first cry for help!

I've had the 2010 848 now for a couple of months, absolutely loving it. Did the 12,000 km service, including checking belts and valve clearances, all went well there and I've been riding it for a good few weeks since with no dramas.

I commute about 90 kms each day.

One day last week, the bike just stopped running while I was in neutral at a set of lights (not running hot). It immediately started again, but I remembered that it happened.

On the way home from work yesterday it did it once again, and then started again. Twice started me thinking.

Then, further down the road, it stopped again while I was riding (outer lane of traffic on the highway at peak hour, of course). It wouldn't restart, so I managed to clutch in and pull over.

It still wouldn't restart, and a quick check of the voltage showed low voltage (less than 12). A few more attempts to restart only resulted in the voltage dropping further after each attempt, to the point where the display would drop out altogether and then restart, so definitely not getting enough power.

Trailer home and put the battery on charge overnight, starting diagnostics this morning.

All fuses okay. Tested via multimeter on the battery, voltage doesn't rise at all with the engine running, just drops slowly, so obviously a charging issue.

Ran through the workshop manual for diagnostics. First test is the alternator. FINALLY got the 3-wire connector unplugged - that took me 15 minutes alone. It was covered in gunge, as is common, from what I've read.

First noticed that the plastic around one of the terminals had melted - not a good sign.

I was a bit confused on how to test the output voltage from the alternator, ever after the workshop manual instructions, but this awesome post from Richard (Punch):
https://www.ducati.ms/forums/241-tech...ml#post3296449

...had me on track.

So I tested the voltages at idle. I know you're supposed to test them at 2K and 6K rpm, but as I had the meter connected and increased the rpms, the values all seemed to rise proportionally, so I figured the relative values at idle would at least give me some indication as to whether or not there was a charging problem.

With looking at the socket (altenator end), I called the pin going in one direction by itself horizontal, and called it pin 1, and the two other pins in parallel going perpendicular to it vertical, and pins 2 and 3 (left to right).

The melted plastic was around pin 3.

The voltages tested at idle were:
1-2: 11.7
1-3: 9
2-3: fluctuating between 6 and 7

To me this indicates the stator is probably junk.

Any advice appreciated.

Cheers!
Michael.
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post #2 of 77 (permalink) Old Dec 17th, 2015, 6:27 pm
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I don't think I'd put a lot of confidence in your voltage readings if you made them through that melted plug. You're going to have to anyway, so cut it off and strip the wires back a little. Make your voltage checks again on clean connections. I bet the mating plug to your VRR looks the same. Hack it off too, and crimp the wires to reconnect using good quality butt connectors and a proper crimp tool. It makes no difference at all which wires connect to which. Three yellow wires to three yellow wires is all you need to care about.

The other piece of this concerning the generator is resistance. You should read Ohms with the engine off in the same manner you read voltage. 1-2, 2-3 and 1-3. You should see a bit less than 1 Ohm. Dead short or open is bad. It is also possible, given the plug was melted, that the wire insulation is also melted or heat damaged along the run from the plug to the left side case. You should check that as well.

The VRR may have failed. If the generator checks out, reconnect the VRR and test the running voltage. If it's no good, this would be a fantastic time to upgrad the VRR to a MOSFET unit.
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post #3 of 77 (permalink) Old Dec 17th, 2015, 7:56 pm Thread Starter
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Thanks Dan.

I haven't yet cut the ends off or investigated the wiring to the alternator housing, but I'm getting what looks like a dead short between all combinations of phases. Is it possible to get a dead short and still have the output voltages I was seeing?

Last edited by forsythem; Dec 17th, 2015 at 8:03 pm.
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post #4 of 77 (permalink) Old Dec 17th, 2015, 8:21 pm
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Quote:
Originally Posted by forsythem View Post
Thanks Dan.

I haven't yet cut the ends off or investigated the wiring to the alternator housing, but I'm getting what looks like a dead short between all combinations of phases. Is it possible to get a dead short and still have the output voltages I was seeing?
Not really. Make sure your meter is set to a scale that is appropriate for low resistance. You're going to see something like .8 Ohms if good. A dead short is going to be zero Ohms. If you are seeing zero, check the wiring for damage before calling the alternator bad. Many (myself included) have replaced that wiring all the way back to the side cover with better, heavier gauge, wire.
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post #5 of 77 (permalink) Old Dec 17th, 2015, 10:22 pm Thread Starter
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0.5 ohms across each pair, but then I get 0.2 ohms when I short the probes of my multimeter directly across each other (?). I had the ohm range set too high when I first tested.

I've cut away the socket housing completely, freeing the connectors. The yellow insulation around the wire that had melted the socket is fairly brown near the connector, but the insulation isn't compromised at all. The rest of the insulation around all the wires right up to the alternator cover is intact (not melted, discoloured or compromised) .

I double and triple-checked the voltages again, with a good contact with the multimeter, same voltage discrepancies.
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post #6 of 77 (permalink) Old Dec 18th, 2015, 7:07 am
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At this point I would try few other things before calling the stator bad. First, actually cut off those connectors and strip to clean bare wire. Might not matter, but clean connections are important when measuring this stuff. Then I'd try another meter just to be sure. You're reading small amounts and many inexpensive meters will struggle here with accuracy. Your readings are lower than I have seen on my own bikes, but still not a dead short. Cut the old plug and connections off the VRR and reconnect to the stator by crimp-on butt connectors and test the DC output of the VRR. Your problems really could have been caused by that melted plug. Many of us have eliminated the plug connection for exactly this reason.

Sure, could be that stator. But I'd go after all other possibility first before cracking open the side cover and $pending on a stator.

I think the 2010 848 still uses that older style VRR? Not one the MOSFET units? Could also be the VRR, they are more prone to failure than the stator. Not sure we've isolated which is bad yet.

This long thread covers the installation of non-standard MOSFET VRRs, There are links in the thread that take you to other sources of info to help isolate charging system problems.
https://www.ducati.ms/forums/80-hall-...-problems.html

My own thread after upgrading the VRR recently on the ST. You don't need to buy new stuff. I've purchased two MOSFET VRRs off eBay, both less than $40.00 USD
https://www.ducati.ms/forums/40-sport...onversion.html
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post #7 of 77 (permalink) Old Dec 18th, 2015, 11:24 am
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Looks like a common stator issue with the 848.



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post #8 of 77 (permalink) Old Dec 18th, 2015, 11:42 am
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Aside from the visual plug damage, which is common to all Ducatis before they went to the better connections and MOSFET VRR, what were your indications? What did you get on your meter for running voltage and resistance checks? The burnt winding on the stator is an obvious visual, but what did you read with a meter across the wires before pulling it apart? Pulling the generator side cover isn't hard, but you have to deal with coolant, the oil, sealant and such. If you can prove out the easy stuff first, that is normally best.

OP's indications are odd in that he has lower than I am used to seeing resistance, but not a dead short. He is also generating some AC that is close to normal at idle. I don't think he gave a value for AC at 4K or higher.
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post #9 of 77 (permalink) Old Dec 19th, 2015, 12:41 am Thread Starter
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Hello again,

Many thanks for all the suggestions and advice so far.

I've cut all the connectors off, bared the wires, and tested from there. Resistance and voltage checks came out the same.

I pulled out the instructions for the multimeter (last resort!), and it's noted that there'll be a resistance of 0.1-0.2 ohms through the probes and wires to the meter itself - subtract the reading from the actual to get the resistance through the circuit tested, so that would result in about 0.3 ohms resistance through each pair tested.

So now comes the bit that has be a bit stumped.

I used some good crimp connectors to connect the wires from the alternator directly to the wires to the RR.

I thought I would test the output of the RR. A quick look at the wiring diagrams shows two positive and two negative outputs from the RR, and the two pairs of green and red/white wires looked to agree. I thought I would do a static test on them without the engine running, to make sure nothing was out of the ordinary. Between either combination of the green and red/white wires, I get a reading of between 7.5 and 8.5 volts, meandering about between those ranges. This is with it not being connected to anything but the alternator wires. I didn't think to check it before I crimped on the alternator wires, but I think I might disconnect them and see if I get the same result.

Am I missing something here, or should I not be getting any voltage reading at all from the RR if it's only connected to the alternator and the engine isn't running? (Ignition off as well) I'm trying to work out where the power is coming from.

A test with the engine running gives voltages fluctuating between 9.5 and 11 volts from each pair, and obviously this isn't enough.

So is the RR only outputting low voltages due to the low voltages coming from the alternator?

And what's with the voltages coming from the RR with the engine not running?

Thanks, one baffled guy...
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post #10 of 77 (permalink) Old Dec 19th, 2015, 4:08 am
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this is my procedure. follow it step by step and don't miss anything, it works best that way. make sure your battery is well charged before assessing the charging voltage at it. i had a brand new lithium battery fuck me over this week due to it getting hissy about being idled until hot. i had to go for a 15 minute ride on the bike to have it give the real reading.

Brad The Bike Boy: Charging system diagnosis procedure
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