Wiring harness beneath the seat. Question.

[Purloined]

A ground wire group of three wires that comes from a bundle that includes a gaggle of wires that plug into the ECU had been wrapped with tape by the previous owner. It looked suspicious to me, so I pulled off the electrical tape and one wire had been hot enough to melt the insulation. I don't know if the routing and grounding of these wires was as originally done, but it was combined with two other wires and grounded on one of the bolts that fasten the ECU to the frame. One of those two wires was a trio of brown/black/white that came out of this harness together, the other ground was attached to the receptacle for a scan tool and the third is the dodgy one. All three, as said, were ganged together after they exited the harness. I'm wondering if anyone might know what device the suspect wire traces back to. I fear it is the Doomsday Machine and I've put everyone at risk, within a certain radius, so it's an altruistic query, but no, really it's more about help in assuaging my deer-in-the-headlights countenance as I peeled it back, even now as I write this. I studied the wiring diagram printed in the manual, it was fun to look at, at first, but my confusion scaled up exponentially. 

I'm thinking another ground could be run from the source. The other wires in the harness were not affected and the other two grounds were fine. The moto operated without hiccup or malfunction despite the monster in the box. And it looks as though the damage to the ground wire was from some time ago, not ongoing. 

There are two pix, one is the aftermath of my chewing through the wiring harness, like a beaver. The other is the happy domicile of the hornets before I kicked it.  okay, only one pic, it won't let me upload the other postage stamp-sized image. I'll see if I can include it in a reply. 

Thanks in advance, any help is greatly appreciated.

[Purloined]

Phew. 

[Purloined]

The more shrink tape I pulled off  the harness to inspect the condition of the fried wire, the more it looked the same. The entire length of the wire is fubar judging by everything I've seen so far. I'm trying to figure where it comes from. I don't know if that is a question that is easy to figure out. And it seems likely that the ground fastened to the ECU (if that is what it is) was not a stock setup.

I started out this afternoon doing a valve adjustment and spark plug replacement, and then, because I'd un-bolted and raised the tank up a bit in order to access the bolts holding the valve covers and the fact that it was 100° in New Haven, the tank expanded and I had to unbolt the seat in order to get it back in place and I therefore noticed a little nonsense in the wiring under the seat. 

I was putting it back together and about to fire it and cool off on a hot day and make sure everything was in order and now it's Vesuvius and forlorn in the garage, for now. 

[Rolf Halvorsen]

If one (by mistake) remove the positive cable from the battery before the negative - it is very easy to touch the ECU with the wrench. Thereby the ground wire from the ECU (directly, but hidden to the negative battery pole) will "be burned" and since the original ground wire is put together with a lot of other cables in a cable loom - all will be partly damaged. 

The solution is easy. Disconnect the original ground wire from the ECU (which leads to the negative pole on the battery) - and replace it with a separate wire "in the open". So if someone later tries to remove the positive cables from the battery -and touching the ECU, without first the negative - the new open wire will get burned alone - and all others will be safe.

Rolf

[MartyNZ]

Have you seen KiwiRoy's picture of what can happen when the main ground comes loose on the gearbox? Could your bike have had that problem sometime in the past?

https://www.v11lemans.com/forums/index.php?/topic/20813-electric-problem/&do=findComment&comment=239405

https://www.v11lemans.com/forums/index.php?/topic/19212-brand-new-guzzi-owner-please-chime-in/&do=findComment&comment=206855

 

[Kiwi_Roy]

Have you heard someone say "When disconnecting the battery disconnect the Negative first", that's what happens if you don't.

Never mind I see Rolf has it covered

I think everyone does it once, the resulting flash gets your attention.

[Purloined]

I looked at the posts that were cited. Thanks for pointing them out. It sounds as though something on the order of what was described is what had previously happened on my bike. 

There appears to be damage to one ground wire only. It is a light gauge wire that comes out of the harness that plugs into the ECU. You can see the connection to the ECU in the lower left hand corner of the photo. There are three ground wires ganged together in this gaggle coming from the larger harness. It was wrapped in electrical tape by the previous owner. Two of these ground wires which had been wrapped by electrical tape were fine. One came from a trio of wires, brown/black/white that were in the harness wrapped as a group, one came off the plug scan tool receptacle (which you can see in the top/middle of the pic), The third wire is toast, the insulation was destroyed as far down as I peeled back the main wrap around the harness, it was horrifying to discover. No other wire seemed to be affected even though they were in proximity.

Is the ground connection to the top of the ECU a normal setup? Would the third (burned insulation) wire be a ground from the ECU to ground? Most of the strands on the burned wire were detached,  just a couple of strands left, but there did not seem to be any problem with the function of the bike. Once I started to un-wrap the electrical tape, the burned wire disintegrated. Does this burned wire come from somewhere else? If so would anyone speculate where? Does it provide a ground from the head of the bolt on the ECU and therefore I could substitute an independent wire from the ECU bolt to a proper ground as has been suggested?

I was an arguably normal person prior to stumbling on this, now my olfactory imagines wires of every stripe are smoldering everywhere. Paranoia sucks. 

[docc]

So, as MartyNZ pointed out, this is what can happen if the main ground at the rear of the gearbox on the right is neglected. Service that well!

The ground on the ECU grounds the ECU case. The crispy wire in the harness comes from up front, possibly the regulator (you should ground that case separately) or the lighting.

[Purloined]

Duly admonished. I'll scrutinize the condition of the ground connections on the gearbox and elsewhere. 

So you're saying that the crispy wire grounds the ECU and leads back to either the regulator or the lighting circuits? To bypass the crispy wire I can ground the terminal on top of the ECU to a proper ground site and leave the burned wire in the harness? 

It appears that the harness with the burned wire turns towards the rear of the bike. 

Thanks to you and all who've offered help and advice. 

[Kiwi_Roy]

The schematic shows several grounds around the ECU but I don't think it shows the one to the case, That one is not required to make the bike run but its general practice to ground any metal surrounding electronics, it helps shield it from nuclear explosions, death rays and such.

The main ground directly below the battery is the most important it should be fixed to a gearbox bolt, some VIIs, mine includes had it attached to one of the screws holding the seat release lock. If the main ground becomes detached when you go to start the bike the starter current tries to find another way back to the battery, often through the long ground wire shown from the Voltage Regulator to battery negative.

When your bike was nice and new the regulator was grounded to the chassis by its mounting bolts. All the charging current over 30 Amp spikes has to find it's way from the chassis to the regulator case so it can get back to the alternator, there is too much resistance in the black wire and you lose some Voltage thats why we add another ground from case to an engine bolt. (this only applies to the OEM Ducati Energia regulators, later ones have a dedicated ground wire)

 

[Purloined]

Wow, Kiwi_Roy, clearly and succinctly stated. Inroads into my puny brain, so thank you for schooling me. Much easier to conceptualize. 

I had a print/copy of the wiring diagram, it was fuzzy, written in Italian in 4pt type, printed in black and white and I believe topped with marinara sauce for good measure; Tolstoy translated into Swahili for my befuddlement, in other words. 

Thx. 

 

[Kiwi_Roy]

Glad you like it, many thanks to Carl Allison for all the work he has done on Guzzi drawings

 

Google Carl Allison drawings    http://www.thisoldtractor.com/guzzi007/sportissimo.html

[Purloined]

Yeah, the drawing was elucidating, far better than what I have.   But I was referring to your lucid explanation. 

[Purloined]

Y'all are in luck, back to me and the subject of my Moto. Ahem. . . 

I cleaned up the wires from the harness that plugs into the ECU, cleaned all the terminals on both battery poles including the ground connection on the back of the transmission case. I abandoned the crisp wire that came from the ECU harness and attached a new ground wire from the mounting bolt on the ECU to a second fastener on the back of the transmission. There are two other ground wires re-attached to the ECU bolt coming from the ECU harness as before.

 Bike starts up, runs fine, but it has a battery drain that started when I had the battery replaced a few months ago. I took the battery out and had it tested and the shop said it was okay. It had been sitting for two days at this point, I don't remember how long it took to run flat before, I think it may have taken longer than two days.

 Before starting it I disconnected the negative leads and, key out, put a meter between the negative terminal and the leads and there was a draw of 22.XX ma on the meter. When I removed the 30 amp fuse the draw dropped substantially. This seems to indicate there is a draw on that circuit? Does anyone have any advice about a possible cause?

The 'abandoned' crisp wire that came out of the ECU harness goes back to wherever it originated, some here have suggested it goes to the voltage regulator, I did not trace it. This battery was not draining when on the old battery. Manufacture date of my bike is January 2000. 

Any advice is greatly appreciated. 

[MartyNZ]

V11 Alternator Regulator.pdf

1 hour ago, Purloined said:

 Before starting it I disconnected the negative leads and, key out, put a meter between the negative terminal and the leads and there was a draw of 22.XX ma on the meter. When I removed the 30 amp fuse the draw dropped substantially. This seems to indicate there is a draw on that circuit? Does anyone have any advice about a possible cause?

The 'abandoned' crisp wire that came out of the ECU harness goes back to wherever it originated, some here have suggested it goes to the voltage regulator, I did not trace it.  

It could be internal leakage in the regulator. See last paragraph of page attached.