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Old 13-Aug-2009, 19:14
cliffwalker cliffwalker is offline
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916 charging problem...yes, another one!

Hi Guys,
I'm hoping someone out there can give me a few pointers with my 916 charging fault.
For quite a while my alternator has only been putting out around half of what its supposed to (at each point in the rev range, the unregulated output reads about half what the manual says it should). As I tend to go for very long rides and the bike is on an Optimate in between rides, I don't usually have a problem. The reduced output seems to keep the battery good enough for a restart or two.
If I ride with my headlights on for any length of time though it seems to be too much for the system and its bump-time.
I've lived with this situation for a year or two and put up with it. I have bought a brand new alternator on good old ebay but not got round to fitting it (2 phase type).
Also (I don't know if this has anything to do with it, but thought I'd mention it) my revcounter seems to please itself whether to work or not. Sometimes it shows a reading but most of the time the needle stays dead.
Last week I was on my way home and giving it some beans (69mph, officer) and the thing just died.
Luckily it was just the 3amp fuse (right hand switchgear and reg/rec)
Because the fus had blown, it was as though the kill switch had been turned on - and the starter wouldn't operate either.
Today, I got the bike out to go for a ride and managed about three miles before the fuse went again.
When I put a meter across the battery there is no increase in the volts when the engine is run and revved (it reads 12.6v regardless). The unregulated alternator output is still half what it should be.
Why is it now blowing fuses?
Has the reg/rec now gone too?
Does the revcounter problem anything to do with it?
Did anyone see the comets last night?
(Sorry, wrong forum)
It looks like now would be a good time to fit the alternator, is the reg/rec likely to be duff now too? What problems can I expect in fitting the alt?
Any thoughts on why my fuses are blowing?

Your help would be appreciated.
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Old 13-Aug-2009, 20:25
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keith888 keith888 is offline
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I'm pretty sure the rev counter on the 916 is electrical not mechanical as on my old bus. Thus, all your problems are likely linked. Low/erratic unregulated alternator output are quite likely to be damaged wiring (from overheating) from the alternator to rectifier. It is important you check this alternator wiring (and particularly connectors) before replacing anything related to charging as this fault can burn out both alternator and rectifier. If in any doubt replace with bigger gauge. If the wiring from alternator to regulator is tested as OK and you still get low unregulated output from the alternator then by all means replace it and recheck. If then OK then reconnect rectifier and recheck at idle. If still 12.6V then its likely the regulator is gone as well so change that before it fries the new alternator :-)

Good luck!

Keith
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Old 13-Aug-2009, 20:37
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Fordie Fordie is offline
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Pound to a Penny, rectifiers dont last that long. My 996 gave me a few non starters at the petrol stations and when I changed the rec/reg every thing was tickeryboo. Certainly check all the connectors around the battery area and the yellow leads from the altenator 4D
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Old 13-Aug-2009, 22:16
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DSC Member Shazaam! Shazaam! is offline
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1. The rev counter will misbehave if the system voltage is low.

2. The fuel pump will draw a high current if the fuel filter is clogged.

3. The alternator output will be low if the insulation is damaged from overheating. Replace the wiring all the way from the engine casing to the regulator. Remove the common sheath that the wires run in, that's where they short together..

For more info:

http://www.ducatisportingclub.com/sh...ad.php?t=78401
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Old 13-Aug-2009, 22:21
cliffwalker cliffwalker is offline
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I forgot to mention in my original post, the charge light had been coming on at low revs but is now on all the time (since the fuse blew). What exactly tells the light to come on?
With regard to the alternator wires, I've already changed them for higher gauge wire where they come out of the alternator cover (leaving about an inch of the original cable), when I tested the unregulated output from the alternator, I put the test probes on the inch of wire that's coming direct from the alternator, so there's no chance its bad/overheated/corroded wires, as I'm testing it practically as it leaves the engine cover and not round the other side near the reg/rec.
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Old 13-Aug-2009, 22:47
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keith888 keith888 is offline
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When you checked the alternator output was it disconnected from the reg/rec? Even if disconnected you could still have a short in the cabling before the disconnect that is losing you volts. Might be worth ruling this out before swapping the alt?

Keith
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Old 14-Aug-2009, 09:14
KeefyB KeefyB is offline
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Quote:
Originally Posted by Fordie
Pound to a Penny, rectifiers dont last that long. My 996 gave me a few non starters at the petrol stations and when I changed the rec/reg every thing was tickeryboo. Certainly check all the connectors around the battery area and the yellow leads from the altenator 4D
Yep!
I had a whole heap of charging troubles on my old 916(1994 bike).The origional finned cast alloy reg/rects are just not up to the job.They are mounted where they are subjected to the heat and vibrations from the engine.The later bikes,used a Japanese unit mounted on an alloy plate for heat sinking.The newer reg/rects also do away with the red charging light on the dash.Ducati used to do a conversion kit from old connectors to new.Not sure if its still available.Alternatively,I have heard good reports on the Electrex units.
If your fuel filter has been changed recently,all the connections good and the alternator wires not melted,then have a look at a new reg/rect.
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Old 14-Aug-2009, 12:37
cliffwalker cliffwalker is offline
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Just to confirm, I'm pretty sure the alternator is duff as its putting out half (or less than half) of what it should be doing (and I'm testing it as close to the alternator as I can get, only one inch of cable coming from the alternator cover).
Therefore the problem is not the yellow cables that run from alt to reg/rec.
What I'm asking is why my charge light is now on and why its blowing fuses within a mile.
I'm quite prepared to change the alternator, as I have a new one sitting on a shelf (and by new, I mean a brand spanker, still in the box) but I'd like to know if there are any things I should know before starting (it seems an easy swop, but I thought I'd check first)
The second thing is, I'm wary of why the gennie light is now on (when it wasn't before, or blew fuses before), what triggers the warning light, as I don't want to fit the new alternator and then find the light stays on, the fuses still blow and I have a different problem to fix.
As I said, the low charging never bothered me too much as most of my riding is long journeys with few stops, so I could put up with it.
What I don't want to do is swop the alternator and still have the problems.
The reg/rec is a separate issue. I don't know if there is a problem with it or not (many of your answers seem to concentrate on the reg/rec, even though I initially said my alternator was duff and didn't mention the reg/rec)
I can't test the reg/rec when my alternator output is wrong (or can I?)
Am I right thinking that the 600 Supersport is the same reg/rec, I know someone who's reg/rec I could borrow if so.
I do have a 3 phase reg/rec from a later bike, can this be used at all or have I got to buy a 2 phase?
Sorry for so many questions but the replies I've got so far weren't answering the original question (why is the light now on and why is it blowing fuses all of a sudden?)
I'm guessing the answer will be that the reg/rec is now also faulty, so that's why the fuses/light etc, but I'd still like to know why?
What signals the light to come on?
I'm thinking a voltmeter is going to go back on the bike when I've sorted it...
I'm having a bad month, my Guzzi seized three weeks ago too.
This is getting an expensive month...

Last edited by cliffwalker : 14-Aug-2009 at 12:45. Reason: spelling mistake
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Old 14-Aug-2009, 12:52
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keith888 keith888 is offline
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I think its likely from what you say that both the alt and reg/rec are duff. As you say you cannot check the reg/rec with a duff alternator (except putting it on another bike) though blowing fuses with a reduced alternator autput suggests it is faulty. Thus, if you are convinced the wiring is OK then you should replace the alt and recheck. If the unregulated output is OK but you still do not have good charging when you connect the current reg/rec then replace the reg/rec and try again. My understanding is that the 3 phase reg/recs will work fine on only 2 phases (try searching the forum).

Dunno how the reg/recs are wired internally but in cars the light comes on when alternator output is less than battery voltage. This could be due to either weak alternator or failed reg/rec so the light coming on doesn't help you much. The fuse blowing does suggest it is faulty though if the wiring is OK.

Keith
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