Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > 748 Charging problems ?

[Wulfie]

Hi Guys,
I don't post much, but do keep an eye on the boards so that's why I'm here as I need a little help. I first started having problems with my 748 SP charging circuit shortly after purchasing it 18 months ago, i'll also add the only problem as well.
I read most of the stuff that Shazaam has posted on the subject so I have a little knowledge and consequently tackled the problem thus.
Firstly, last year I had initial problems, so I inspected the wires from the alternator connectors to the RR, they were found to be brittle and corroded so I replaced the wiring from the altenator connectors to the RR by soldering uprated wires (30A capacity) to the original ones from the alternator which looked OK. Then the replacement wires were individually covered in heat shrink and then both fed into a heat protective tube and the covered in heat shrink to tidy them up. This cured the problem for last year.
This year after winter the bike was slow on the starter and popping etc so I bought a new Bosch battery, at the pricely sum of £70 too but that sorted that out. this was about 3 months ago. I went out on the bike 2 weeks ago and it broke down again, incidently the bike has had weekly use at least since the battery replacement with no problems.
I suspected the RR would be U S as the current provided from the alternator, which is a single phase alternator was measuring OK, and the measurement across the battery with the engine running was only 12.5v with no increase to the voltage upon increasing the revs, so I have replaced the RR with one from ebay ( I know, I know but we'll get to that later) upon fitting the replacement RR and checking the current again I have found that when the bike is idling the AC current from the alternator is @ 70v, when you increase the revs to 6000 rpm @ 120v, a substantial jump from the last measurement ? (just to confuse the issue I have bought a new better meter in between the measurements so I am assuming that the new measurements are correct. however I have no proof at this point.) however the regulated voltage is still about 12.5 v.
So here are the questions....and thanks for reading so far
1 Are there any circumstances that the alternator would dish out more AC voltage than the RR can handle thus knackering it, and explaining why the readings are the same with either regulator fitted ?i.e both been cooked.
2 Are the AC voltage readings acceptable at those levels, as the upper one is ball park with the manual, however the lower readings seem high ?
3 What sort of fluctuations in voltage are normal when testing the AC current ?
4 Would a gunged up fuel filter cause a low rectified voltage reading and potentially if replaced could this solve the problem.
5 Would you still get a voltage reading of @12.5v from the RR conectors back to the loom, i.e after the rectifier if it was not working at all ?

Of course I am aware that the RR I bought from ebay could be goosed same as the original one, and of course it stands to reason that this is probably most likely, however I am reluctant to spend £70 on a new one just to have something else render it useless as soon as I fit it, if you follow. It's a bit rambly I know but thanks for reading anyhow.

Cheers

Wulfie

[skidlids]

The Alternator should make maximum output when New/In Good Condition, if it has a fault such as a short across some windings then its output would be lower, so I can't see how it could put out more and hence damage the Rectifier/Regulator.
Have you checked the condition of the Charging fuse (the 40A large one)and its connections to make sure the voltage output from the regulator is getting to the battery

[Wulfie]

Yep,
That's what I suspected with the alternator, I can't think of any reason why the voltage would increase, mind you I don't fully understand it all
I had a good look at the large fuse situated at the side of the battery last night, it was pretty cruddy to be honest so I dismantled the connector and had a bash at cleaning up the female connectors and the lugs on the fuse, the voltage accross the 2 wires was again 12.5v, however I couldn't crack the bike up as it was getting late and it's loud as a ******* and half the street had their bedroom windows open plus her indoors would have looped .......ooh the temption.
I take it that this fuse is between the RR and the battery then to prevent an overload if the RR has a wobbler ? although mine's on 30A ??

[DEMON]

here are some quick notes :-

1. if you were to measure the dc voltage at the battery at idle you will prob find it to be around 12 - 12.5 volts. Rev the bike up to 3-5k revs and it should increase to around 14.5v dc.
answering your questions :-

1. Substantial voltage from the alternator - unlikely unless you had a problem in the windings.
2.The AC voltage readings are more or less correct, but you dont mention any rpm values to cross check these. A new gen would poss give lower readings.
3. You are measuring voltage not current wulfie, and the AC voltage fluctuations are normal, changing in relation to the engine speed.
4.A blocked fuel filter will cause engine running problems more than affect the voltage. If your bike is running rough, then it will efect the output from the alternator accordingly
5 you could and this could be battery voltage.

a good check of all your connections is required, both batt side and reg side to ensure you have no points of high resistance. check your earths etc too...let us know what you find ?

[Wulfie]

Originally Posted by DEMON

here are some quick notes :-

1. if you were to measure the dc voltage at the battery at idle you will prob find it to be around 12 - 12.5 volts. Rev the bike up to 3-5k revs and it should increase to around 14.5v dc.
answering your questions :-

1. Substantial voltage from the alternator - unlikely unless you had a problem in the windings.
2.The AC voltage readings are more or less correct, but you dont mention any rpm values to cross check these. A new gen would poss give lower readings.
3. You are measuring voltage not current wulfie, and the AC voltage fluctuations are normal, changing in relation to the engine speed.
4.A blocked fuel filter will cause engine running problems more than affect the voltage. If your bike is running rough, then it will efect the output from the alternator accordingly
5 you could and this could be battery voltage.

a good check of all your connections is required, both batt side and reg side to ensure you have no points of high resistance. check your earths etc too...let us know what you find ?

The voltage across the battery doesen't move from idle to 6000 rpm

RPM Voltage Values
tickover @ 70v
6000 rpm @ 114v +

Checked all the continuity on all wires came up OK, no leakage from the battery and across the alternator wires. All connections good.....spoke to the guys at Forza Italia yesterday seems like the common concensus is some numpty bought a dud RR from on ebay when he should have bought a new one........doh...

New one ordered, no biking for me this weekend.

Edit - the guy has offered me my ackers back, so no damage done I suppose

[Shazaam!]

Checking the stator wire's continuity won't reveal the problem.

The error that most people make is replacing only the 6-inches or so of the crispy portion of the stator lead wires adjacent to the connector. Even though not visibly damaged, the adjacent section of wire should also be replaced with a larger gauge all the way back to where it enters the engine casing. This is because the entire wire has been overheated and has lost its electrical insulation properties which then allows the wires to short together (likely within the common sheath), usually at the higher voltages produced at higher engine speeds but sometimes also at lower rpms.

This lead wire shorting in the sheath area will damage the regulator's solid state components. Remove the sheath and use stand-off insulators where the wires come near any grounded component.

[DEMON]

Good...sounds like you are getting to the bottom of the problem now, cant believe you were sold a dud on ebay, shazam's help too will guide you to a working bike shortly...hang in there, at least you are not offshore 6k miles from home with 3 bikes in the garage doin nowt !

[Wulfie]

Originally Posted by Shazaam!

Checking the stator wire's continuity won't reveal the problem.

The error that most people make is replacing only the 6-inches or so of the crispy portion of the stator lead wires adjacent to the connector. Even though not visibly damaged, the adjacent section of wire should also be replaced with a larger gauge all the way back to where it enters the engine casing. This is because the entire wire has been overheated and has lost its electrical insulation properties which then allows the wires to short together (likely within the common sheath), usually at the higher voltages produced at higher engine speeds but sometimes also at lower rpms.

This lead wire shorting in the sheath area will damage the regulator's solid state components. Remove the sheath and use stand-off insulators where the wires come near any grounded component.

Thanks Shazaam.....I had considered that a common sheath for both wires may not be a good idea (unfortunately after the fact) so when I get to fitting the New RR I'll probably do the wiring right back to the alternator stator, although the tests aren't showing up any big problems in the outputs at the moment, better safe than sorry. No doubt i'll keep you posted

DEMON - I can give them bikes a workout for ya if you like

[Wulfie]

Fitted new wiring from the stator to the RR last weekend.....sorted

Thanks for all the advice guys

Chris

[DEMON]

Originally Posted by Wulfie

Fitted new wiring from the stator to the RR last weekend.....sorted

Thanks for all the advice guys

Chris

aboslutely mate..get yourself up to the North of England and we will show some of the great roads round here!!