Regulator/Alternator Problems

JohanM · Post by **JohanM** » Sun Jun 21, 2009 4:20 am

History: Have a 900 S2 1983. Dad bought it new. Over a period of 10 years the regulator burnt out 4 times. Took the bike in to Ducati SA to sort problem out. Changed the alternator (Changed 3 phase to 2 phase), regulator and wiring. 3 burnt-out regulators later the bike stood in a garage for a number of years.

Bought the the bike to redo. Redid all the wiring etc, etc... bought the regulator from bevelheavel shop. Did all the prechecks, got the road worthy and ready to go. 50 km later the regulator was smoking, another regulator gone!!!

Does anybody know if this is a common problem with the 900S2 and what can be done to rectify this? I'm open to any ideas.

O,yes. The regulator, alternator was working fine/correctly after it was initially installed.

Thanks
Johan

wdietz186 · Post by **wdietz186** » Sun Jun 21, 2009 9:15 am

Johan,The charging systems on these bikes are pretty reliable and simple.I would suspect a grounding fault is the problem.Paint or powdercoating can insulate the engine from the frame and will cause all sorts of issues.I'm not sure of the arrangement on the S2 but there should be a cable from the engine to somewhere on the frame,make sure the connections are clean bare metal to clean bare metal.Star washers will help ensure a good connection.If there isn't a fairly heavy gauge wire from engine case to frame it is time to add one.The same goes for the ground wires in the harness,clean connections and star washers.The regulator case needs a good ground also.A wire from it's case to the neg. battery terminal wouldn't be a bad idea.Also make sure the connectors from the alt. and reg. are clean and tight.

Lumpy · Post by **Lumpy** » Sun Jun 21, 2009 1:02 pm

Not sure about the S2 but on my bikes there is a ground wire from the reg terminals that contacts the frame by one of the bolts hoding down the reg. I`ve had issues with bad earths there. mind you both mine are after market regs.
I`m no electrician but I would also check that you don`t get continuity from your alternator windings to the engine cases. I`m only guessing here but I would assume that to be not a good thing.
You mention the wiring has been replaced, was it replaced as it came off or did you go by a wiring diagram? I guess if there is a wiring issue you would only repeat the problem by wiring it the same way.
I`m guessing you get a normal charge rate of say 13-15 volts when you give it a rev. I know on mine if I go for a good run you will see bubbles rising up through the battery electrolite.
A test light is a wonderful investment, in particular for for the Ducati owner. You can trace your way down wires from connector to conector to pin point faults. Mines like an American Express, I don`t leave home without it. Lives in the tool tray.
One last thing, not sure of the fuse box`s on S2`s but if they are those standard glass tube fuses rip it out and ditch it for a blade fuse holder. They are cheap as chips at your auto shop and much more reliable. I had my head light go out half way round a bend thanks to those old crappy holders Still scrubbing the stain out of my leathers from that one!!!!!

Peter Mille · Post by **Peter Mille** » Mon Jun 22, 2009 11:41 am

I had the same issue with my Mille!
The regulator exploded while driving with a noise like someone shot at me with a gun.....the alt. light came on, and I stopped and was shaking from fear (remember, at a Mille MHR, the regulator sits under the gouges, near your face...!!).
After replacing the regulator with a new one, the Dutch importer told me to mount a wire, directly from the regulator ( there is a "ground" symbol on it near one of the mounting holes!!) to the - pole of the battery, to have a good ground, after that, no more problems!

Lumpy · Post by **Lumpy** » Mon Jun 22, 2009 12:24 pm

Now you got me worried. My regulator sits straight underneath my family jewels. I`m pleased to say mine has an earth strap directly to the frame via one of the mounting bolts..........................the regulator..............not the family jewels...................

nottonight68 · Post by **nottonight68** » Fri Jun 26, 2009 4:45 am

the enemy of the regulator is internal heat build up-hence the fins.they need to be in the wind(so to speak).they also use the bike frame as a heat sink-paint on the frame under the reg can reduce the heat sink effect.

machten · Post by **machten** » Fri Jun 26, 2009 9:22 am

I'm not sure of the arrangement on the S2 but there should be a cable from the engine to somewhere on the frame,make sure the connections are clean bare metal to clean bare metal.Star washers will help ensure a good connection.If there isn't a fairly heavy gauge wire from engine case to frame it is time to add one.The same goes for the ground wires in the harness,clean connections and star washers.The regulator case needs a good ground also.A wire from it's case to the neg. battery terminal wouldn't be a bad idea.Also make sure the connectors from the alt. and reg. are clean and tight.

Smack on the money. Check your earth. Star washer - yes - especially if you have powdercoard the frame.

Kev