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Discussion Starter #1
I bought a Ducati 916 1997 and it does not charge the battery. The readings when the bike is Idle are 12.3v after i stated it, and it does not charge while its idle.
The two yellow wires read at around 15.6 on AC setting when they are idle.
When i rev the engine the battery's voltage goes up to around 13.5V. And it does not go higher than that. I raved it up to 11000rpm and the voltage still 13.5.
Also when i rev the engine the two yellow wires read at wound 15.5 AC and it does not go higher even when i redline the engine.

I have been tryn everything the battery is brand new and it gives out 12.7V. Also when i crank the engine the battery's voltage does not go lower than 10V. Bought a new Rectifier and i changed it but still same story.
What do you guys think the problem is?:confused:
 

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Old Wizard
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3,006 Posts
Common problem.

The regulator voltage output is OK. 13.5 volts is adequate to keep the battery charged.

The AC voltage output of the stator should increase with rpm. It doesn't because the insulation on the stator wires is heat damaged causing them to short together at the higher stator output voltages.

Ducati charging systems have stator wires that are seriously undersized and they overheat. In particular, the in-line connector develops a high resistance from being either too loose or from corrosion, and they heat-up and melt the plastic connector and damage the wire's insulation.

The rule-of-thumb for sizing wiring is that if it needs to carry 20 amps use 12 gauge wire; 30 amps needs 10 gauge; 40 amps needs #8 gauge. Early bikes have 350 watt/29 amp two-wire charging systems so 10 gauge should be used.

These wires have to pass high amperage continuously. There’s an electrical phenomenon called I-squared-R loss. That is, if you run 30 amps through a corroded or loose connector having (say) a 1/2-ohm resistance, the heating effect is 30 X 30 X 1/2, or 450 watts. That’s a lot of continuous heat. This heat just conducts down the wire, cooking the insulation as it goes.

Just like you can’t put your hand on a 450 watt light bulb while it’s lit, you can’t expect a plastic connector to survive radiating 450 watts of power either. A corroded or loose connector always has a higher resistance than the adjacent wires and it will heat up enough to melt connector plastic parts and nearby wire insulation. That’s why it’s best to solder the wires directly together and eliminate connectors entirely.

It is the connectors heating up that caused the insulation and conductors to melt and short out.

On my 916, for example, the stator wires got so hot that the insulation became brittle and cracked near the regulator connectors. A closer examination showed that the damage extended along the wire all the way back to the engine casing. I could scrape off the softened insulation with my fingernail.

Shorting the stator wires is one of the primary causes of regulator damage.

Stator Wiring Replacement

http://www.ducati.ms/forums/showthread.php?p=676579#post676579
 

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Discussion Starter #3
thanks for the reply shazeem. The connectors look good and the previews owner sayd the dealer changed them and rewired. I cleaned the connectors and all the test i did was behind and in front of the connections and i got the same readings. Do you think the wires are burned where they connect to the stator? Also the wires go all the way to the side cover of the engine. Is the stator inside the cover. The cover has some kind of a seal. If i decide to take out the cover how do i put it back? thanks again.
 

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stator output

unplug the yellow wires and run the engine read the ac output of the unpluged stator from yellow to yellow it needs to output above 50vac when rever up you should not have to go above 6000 rpm if the output is lower than 50 vac then the stator is bad what year is the bike and which regulator rectifier is on the bike the bare aluminum one or the black one
 

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Discussion Starter #5
The regulator is the stock gray one. The bike is a 1997. I measured and it does not go higher than 15.6vac. but the battery does go to 13.5V.
 

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Old Wizard
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Later stators have the common sheath extended all the way to the inside of the casing. So yes, the lead wires will touch and short-out inside the casing. If the leads were replaced only in the region outside the casing you'll have to pull the cover to replace the leads.
 
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