916 Regulator/Rectifier possibly shot?
 

Hi all,

I know this one has been done extensively and I've had a quick read through the old posts.

I just wanted to post up my particular symptoms before I order a new RR51 in case it's anything else and I'm being dumb!

Firstly, I've attached a picture of my current R/R as I'm not sure if it is the early or late type. (I know it's undone with the earth strap off, I was re-fitting it after checking all the wiring when I took the picture :))

Basically the bike runs fun with the lights off and I can blat round as much as I want.

On the way home from the cafe on Wednesday it was getting dark so I switched the lights on and it started playing up, misfiring etc. within a mile or so and stalled shortly after. I managed to get it home after a bump start but it was running like a bag of nails (much to my wifes amusement when I got home :))

I've checked all the wiring and it's all fine, nothing melted, shorted or anything but the R/R does run very hot even at idle.

I decided to re-locate it under the seat unit to get it away from the exhaust and it still runs hot even at idle. It also does not appear to be pumping much more than 0.5v into the battery @ 3k RPM but the battery is fully charged and very healthy so I'm not sure if it should. I can't seem to get it over 13v though so I don't think it is charging.

Took it out again yesterday and everything was fine, she is a little honey, and on my way back, about a mile from home, I decide to turn my lights on after maybe 60-70 miles total riding and within 100 yards she is popping loudly on overrun. About 200 yards after that, even though I switched the lights off almost immediately, she starts running rough and I barely get it home - stalled about 50 yards from my door :(

To my mind it is either battery, R/R or generator/stator.

The battery appears to be fine, charges well and holds 12.4 volts no problem.

I can't see any obvious problem with the generator/stator so it has to be the R/R?

Sorry for the long post, I just want a bit or reassurance before I order the new one later today.

Many thanks!

Phil

Do you have to re charge the battery each time this happens? With the motor running there should be about 14.5 volts across the battery at 3000 rpm. Significantly less than that then you have either an alternator or regulator problem i think.

Is the engine quiet? Is there any noise from the left hand side that doesnt go away when you pull the clutch in?

I am thinking that this is not just a regulator problem. Rockhopper is right that there should be over 14V across the battery when charging, and on mine I think there is 11.7V when engine is off.

The other symptoms you describe seem to suggest there is something mechanical going on too. Was it only the STs that had alternator rotor nut problems? I do not know enough about the 916 series to comment.

A short in the alternator coils would also cause problems with the "back EMF" which would have a tendency to fight against the engine. Not sure how much that would be noticable and give you a feeling of "running like a bag of nails".

We're sure this is "bag of nails" is not normal Ducati clutch rattle? My ST2 was described as "dragging a shoping trolly down the street"! :frog:

Phil, yours is the old style. If you fit a new style or the RR51 from Electrex, I would also fit the heat sink that the newer bikes have.

Electrex have a nice fault finding chart here. I'd start with that.

The ST4 shares the 916 engine (mostly) so suffers the same nut problem. Its even cropped up on at least two M600's that i know of.

Cheers guys.

The rough running is as though the ECU has gone into 'limp home' or safety mode.

Massive bangs on overrun, very hard to accelerate, won't idle and flames out of the exhaust!

The battery is fit and I do keep it on a trickle charger, it has needed recharging after both of these rides.

It runs absolutely beautifully before I turn the lights on which makes me think the additional load is more than the battery can handle because the R/R does not seem to be contributing enough to charge the battery.

Is there a quick, visual way I can check the alternator nut? It was serviced 500 and 900 miles ago by 2 different dealers (big £'s) and given a clean bill of health each time.

Cheers!

Phil

I dont think the ECU has a limp home mode, its not that sophisticated. Sounds like there isnt enough juice to keep the fuel pump etc running.

Depending on how loose the nut is you might be able to see bits wobbling through the left hand sight glass or there might be a noise that doesnt go away when you pull the clutch in.

You need to check what was actually done at each service, they dont all do the nut unless you ask them as the side cover needs to come off which means dropping the oil and coolant.

Really sounds just like a cooked regulator.

Agreed, I'm going to run through the fault finding chart that Felix pointed to and go with a regulator initially if it points that way.

If that doesn't fix it I can then move on (probably to a specialist) and get the other bits checked out.

Any other thoughts still appreciated though.

Cheers!

Phil

Check the earth connections are sound including the engine earth strap.

Good point, I've already redone the ones to the R/R when I moved it.

Phil

If the alternator nut was loose it would run badly pretty much all of the time not just when the lights were turned on. I would check the casing on the l/h side and see if there's new sealant on there which would indicate that it's been removed and probably tightened though, or ask the dealer(s) who serviced it ;)

Yep, failed R/R according to the tests.

The generator/stator appears to be fine which is good news.

I've just ordered an R/R from Electrex after speaking to Miranda and I'd like to say their customer service is excellent.

Out of interest, a Ducati R/R is £136 and 2-3 days wait and the Electrex is available next day by special delivery for £75 so it's not a difficult choice.

The customer service from Ducati Ashford was very pleasant as well though.

Many thanks to all who helped!

Phil

Do fit the later style heat sink plate, though.

There's a high current involved here so you need to run separate ground wire from the regulator in its new location back to the battery terminal. If you grounded to the frame locally, that's your problem. Any regulator normally runs too hot to touch which is why you should place it out in the airstream.

The under-the-seat location might be better than inside the fairing but I recommend the backside of the license plate holder. Under the seat has poor heat convection and conduction cooling (unless you use a heatsink bolted to something cooled by the airflow.) The "heatsink" plate added to later bikes is there primarily to reflect exhaust pipe heat away from the regulator and help direct airflow from the fairing duct. It won't help much under the seat.

The charging voltage will be different for different batteries. Mine typically runs around 13.6 at speed. If the battery terminal voltage is higher with the lights on at 3500 rpm than the voltage at key-off, you're charging OK.


http://ducatisportingclub.com/contro...d.php?tid=2042

Nice one, good idea to take the earth back to the battery.

My new Electrex R/R should be here Friday so I can get cracking.

Is there any issue with riding in the wet if I mount the R/R on the inside of the license plate holder?

I don't actually ride in the rain deliberately but could get caught out.

Many thanks!

Phil

The RR51 electronics are encapsulated in epoxy so it's waterproofed, but I suppose adding a little silicone sealant where the wires exit the regulator casing wouldn't hurt.

There is no way I would mount the regulator that far away from the battery. For good reason you want to keep the wires as short as possible. But hey, to each their own.

When you relocate your regulator to behind the license plate, the stator wires are routed outside (the hot environment inside the fairing.) and you use a larger AWG 12 gauge wire to compensate for the somewhat longer length and electrical heating due to the high current being carried.

The main issue with replacing the stator wires is to reduce the electrical heating from the 30+ amp current they have to carry. A different aspect of this is that any in-line connector becomes a hot spot because, as corrosion occurs, that causes the connector resistance to increase and the heat generated to increase in this region. This damages the connector (melts the plastic ones) and overheats a few inches of wire both sides of the connector.

But that’s not the whole issue. Any wire, no matter what size, has resistance (so many ohms per foot) so any wire will heat up. Obviously the larger the wire gauge, the less resistance it will have to current flow, and the less heating that will occur for a given current.

The type of insulation on the wire is also important to this discussion. Different materials have different temperature allowables for continuous operation. For example for 10 gauge (AWG) wire in 30ºC (86ºF) free air:

55A will heat high density polypropylene to 90ºC allowable
58A will heat Polyvinyl Chloride (PVC) insulation to 105ºC allowable
75A will heat Kapton, Teflon, and Silicone insulation to 200ºC allowable

So for example, silicone insulated wire should be used for higher current ratings or for hotter operating environments.

The environment that the wire sees is very important, and this is where Ducati engineers screwed-up. The above temperature ratings assume that the wires are located in 30ºC free air. The stator wires run first internally to the engine, and then are enclosed on a sheath that passes over the engine and internal to the fairing. So the insulation on these wires don’t see adequate cooling, they exceed their performance rating, and loose their insulation properties.

The portion of the stator wiring that run in the sheath is where insulation failure is critical. The stator wire are held closely together and insulation breakdown from heat causes them to short together at the higher output voltages at higher engine rpm.

The Haynes Manual, Section 9.21 has this warning:

Caution: Never disconnect/connect (i.e. short together) the alternator wiring with the engine running as this will damage the regulator/rectifier.

Most regulators fail because they get too hot inside the fairing, but this intermittent shorting together of the stator wires is the other cause of regulator failures.

The wires inside the engine don’t come in contact with each other until they exit the cover. Even if the insulation overheats it can’t damage the regulator, and because of the hot environment, a larger gauge wire inside the cover isn’t going to reduce insulation operational temperatures much in this section of wire.

The leads attached to the regulator/rectifier are a smaller gauge but they also see a cooler environment than the sheathed wires. Sure, they’ll be heated more than the larger gauge replacement wires but they have better cooling. So, just make a low resistance splice to the RR wires.

On my 916, I relocated the RR so that the stator wires now quickly exit the fairing, run along the frame (good conduction and convection cooling) and since the regulator is outside the fairing it runs much cooler. So this situation allowed me to run a only slightly-larger 12 gauge (SWG 14 gauge) PVC coated replacement wire between the stator cover and the regulator splice.

Excellent service from Electrex, my R/R arrived this morning even though I only ordered it yesterday afternoon.

I'll be off shortly to pick up some decent wire and I'll try the license plate location initially I think.

Many thanks to all who helped.

Phil

All fitted now and charging perfectly.

Went with the original location in the end (couldn't get decent cable) and made an ally heatshield up which is isolated from the R/R.

Nice to know I can have my lights on now!

Cheers!

Phil