Popped in the shed to give the bike a look over ready for an early doors start tomorrow and found all was not well. All but one of the battery top up plugs have blown out splashing acid about, luckily quite locally. What wasn’t so lucky was the cause. Tried blowing through the breather tube with no joy so off with the battery for a better look and found a melted battery tray and burn marks on the back of the battery. So gently off with the battery tray and… The last time I was out a following mate had said the indicators were blinking faster as I accelerated but had been fine earlier, that’s the cause of that issue covered I would think. Oddly where he first noticed the indicators playing up suggests that if the cause was the fire, I was still able to ride a further 100 odd miles home none the wiser. It seemed unlikely but scenario two would be that it happened after I turned it off and put it away which seemed less likely still. So, after a drawn out mental should I shouldn’t I session curiosity got the better of me and I put the battery back and turned it on. Nothing caught fire nothing went bang and nothing made an expensive phutt sound accompanied by a small mushroom cloud of ecu smoke. In fact It fired right up like it was a mere flesh wound and was raring to go. Needless to say I turned it off sharpish but it does beg the question, do Ducati fit fuses because they’re a nice colour?
That connection is a well known fault on the 748 along with the two cables from the generator overheating. Steve
Bad luck Ian , thats that feckn connecter block thats stuck to the back of the battery tray , they get dirty and damp and then heat up and melt .
You’re quite right guys about that connector and it should be my first suspect but I’d had it replaced 18 months ago. I also clean all connectors every winter so I know it was clean and in good order, it hasn’t got wet this year either. That said it was2.5 k miles ago and things can of course fail at any time so it has to be suspect number one. If you look to the left of the pic however you can see the side stand bypass connections ect are also in a real molten mess. That surprises me because it lines up with the melted hole in the tray and burn marks on the belt covers and appears to have been the hottest point so I’m not convinced what caused what just yet. Could be I have got some cable routes wrong/trapped and something has fretted through. Whatever did happen the fuses are all correct sizes and intact You have to laugh though because the only spares I carry with me are full set of bloody fuses:Banghead:. Full investigation tomorrow.
V. Lucky escape, it's not just that plug that can cause high resistance/overheating but also the size of the wires that run between the regulator and the generator as they are only just up to the job plus the copper can degrade badly over the years. What might help to confirm this would be to look at the yellow wires as they emerge from the alternator for signs of overheating/distortion and if the insulation is on the verge of falling off the wires in places.
Mine was over heating a lot, even with a good clean of the terminals. Was getting really concerned so opted for a replacement rectifier. Was on the Isle of Man at the time and the 1 and only dealer didn't have one...said I could try an 848
AH now that’s interesting Chris. I’ve been concentrating on the connector over the years thinking the wiring of later bikes was ok when I should have been thinking marginally better by the sound of it. Once I’ve had poke about and cleaned it up I’ll do as you suggest and see if get any clues. Whatever the outcome it needs sorting properly so I’ll be looking for a better set up rather than replacement parts and someone sharper than me that’s already got it sorted out.
It’s well past the try a new rectifier stage…sorry I couldn’t resist, I know full well what you mean and I’ll check/replace it.
[I have to say this Rob] - the search engine on here is terrible but if you could find threads relating to this they are manifold on here Ian - "Denzil" has some very useful input on here also.
Ian, bad luck, that is a mess. I think your problem started with the ac connector which unless it is entirely clean, dry and very tight will eventually break down due to increasing resistance generating heat- generating more resistance and even more heat. One of the pins got hotter due to a slight resistance(this can be as low as 0.5ohms)and it snow balls. This eventually sent the rectifier into overheat due to an imbalanced three phase supply, only 1 of the three pins would have been burnt at that stage. The regulator then failed to high voltage, at a guess 19v - 20v DC, boiled the battery (they cant cope which much over 16v) and then anything that was in the way and live (like relay coils on a side stand relay) probably overheated or melted/fused, before you know it the bike is dead. ECU is quite resistant to damage as it 'conditions' its supply to provide a stable operating condition, excess voltage there would be dumped as heat. As I have posted many times the 3ph stator to reg/rec connector should be cut out and the wires either soldered or replaced with clamping high amp connectors-NO bullet connectors as they are worse than sh!t. I do not agree that the cables are too small on the 3ph systems, everyone ignores (or is unaware of) three phase electrical theory which means those AC wires will only see maybe 4A 100v AC on full load. Regarding the fuses, as the problem is entirely on the power supply side, until it becomes so serious that you melt wires or services - no fuses will blow I had the same problem on mine but discovered it early due to a slightly eggy smell from the battery when it boiled. Only one of battery cells casings was melted through and as the battery was AGM the acid loss was minimal. Not much acid damage was done and most of the acid remained in the absorbent glass matt, the battery continued to work and read out a healthy voltage except when the engine was running. Mine was reading 12.8v at rest, 15.9v at tickover rising to 19v at 2500rpm. Before then I always remember the reg getting very hot and thought it was normal. Since soldering each yellow wire the regulator has never even got past warm. Since that incident I have the battery voltage indicated by a voltmeter on my dash and regularly feel how warm the reg/rec gets to monitor the health of the system. When you get yours repaired make sure you use automotive spec cables and if you rewire the ac generator wires make sure you get oil and temperature resistant ones. Most folks that rewire use normal cables which will deteriorate quite quickly due to the heat and petroleum Hope the the damage is limited and the repair quick and inexpensive
Longest post this year :smile: We will just have to agree to disagree on the wire size/quality, I have had similar problems but with plug clean/intact and have opened up insulation to find a sticky corroded mess. Totally agree on everything but.
Well i’ve spent a few educational evenings searching old threads and jeez! Denzli, Chris and the other tribal elders must roll their eyes when this problem crops up. Denzil, I hope it wasn’t too tedious typing it all up AGAIN! I do appreciate that you’ve expanded on the points covered and I now understand correctly both what and why. Other than my connections were clean and dry (can’t vouch for tight as not tested) Denzils ideas of events I feel are as close as you’re going to get without sitting there watching it happen. I also think Chris’s experience has a bearing as although my generator wires appear ok the leads from the connecter to the rr do have green corrosion to the top two inches. Although only light it is there and if the connection wasn’t as tight as it needs to be as well then… My plan is to rewire from the generator with the appropriate spec but I’m unsure of the gauge needed. I’ve read Chris and Denzil’s thoughts on this and find myself agreeing with both depending on the scenario, so if anyone can tell me what is the gauge fitted from new? and what would be a sensible increase? that would be a real help and I can mull it over some more. I’ve snipped the plug off the generator wires while the only thought rattling around my head was its shot and it will be easier to pull the wires through and made no effort to look at what went where. I’m thinking all yellow and all from the generator maybe it doesn’t matter? As far as damage goes I’m looking at, new battery (sealed), lower belt cover, r/r, battery tray, side stand switch bypass, mid main loom and possible flasher unit. The worst of that is my replacement alarm bought in May is spliced into that section of loom and unless I come over all brave will be redundant. Oh well could have been much much worse so feeling more lucky than not.
