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Grounding Voltage Regulator


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Recently I have been seeing the red charging lamp flickering on while riding down the road. I decided to run an additional grounding wire from the regulator to an engine bolt, a screw on the altrnator cover to be accurate. About 8 inches of wire, and 2 ring shaped electrical connectors were all that were required, as well as 15 minutes time. The flickering has ceased, at least for now. The odd part is how much better my Guzzi runs! It has always run just a little cobby from idle to about 2K rpm. I have always thought it was just poor ecu mapping, I have the factory performance one. I read about poor mapping all the time on current motorcycle tests in magazines. For instance, this bike was a little difficult to putter around a parking lot at a walking speed, sneezing, snorting, and near impossible to be smooth with. Since installing this wire, it is very smooth down in the lower rpm range, much easier to let out the clutch from a standing start, and quite a bit more civilized overall. Why didn't I do this sooner! I do wonder what exactly I did affect with this grounding wire. I suspect that a smoother or constant voltage to the ecu, ignition, or FI must be at work here. The original grounding wire, from the wiring harness, was indeed securely fastened to a regulator mounting bolt. Obviously it was not adequate. I have had no weak battery issues in the past. It is quite important to make sure the engine, frame, and battery negative are all well connected.

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That is interesting. I have a theory: Before doing this you had a much more fluctuating system voltage at lower revs. The injectors will react to that, lower voltage means slower opening. You always have a lag (typically in the order of one millisecond) between the electrical pulse and actually squirting fuel. This is called "injector dead time" and is compensated for. The ECU should have a compensation table for dead time vs voltage, called "battery compensation" or something like that. If this is well done, the effects should be small so maybe the OEM ECU has a poorly implemented compensation.


I haven't found any specification for our injectors but typically there can easily be an added lag of 200-400 ms if voltage goes down a couple of volts. Uncompensated, this can make up for a 5-10% change in mixture at those revs.

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Hi Buzzard, Raz


This is interesting for me too.

I just have a Breva 750 im my workshop that shows sometimes poor power when accelerating. While doing a fault readout of the ECU with an Axone tester at the local dealer, we evaluated the voltage at the battery never went above 13 - 13,1 V. There were no faults stored in the ECU and the TPS was zeroed corrrectly. The Breva regulator is directly connected to the battery negative terminal, so an additionnal groundwire was not the true solution for this. With a new regulator the voltage increased to 13,9 V which is enough to laoad up completely the battery. There is slightly more to come when the engine runs for a longer time - just tried it in the workshop for a minute.


I'm curious if the power losses are gone with that measure too...

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The Breva regulator is directly connected to the battery negative terminal, so an additionnal groundwire was not the true solution for this.

I think that a ground wire to the engine block, in addition to the battery-regulator connection, is a good idea.

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Ha, finally someone has realized what I have been rabbiting on about is correct.

The grounding of the regulator is VERY important, All of the alternator current passes back through the ground.

Actually the regulator doesn't regulate the battery voltage, it regulates the voltage between it's case and the black wire to 14 Volts or thereabouts. If you have a poor ground at the regulator it's the battery that looses out (1/2 volt lost in the ground is 1/2 Volt less that the battery will charge too)

The two spring nuts are not good enough to provide a good ground, you have two dissimilar metals getting sprayed with water and road salt or whatever, that's just asking for electrolysis. For my ground I drilled a 1/4" hole through one of the fins and attached a wire with a bolt slathered in grease. The other end I connected to a timing cover bolt.


Charging Circuit.pdf


"Recently I have been seeing the red charging lamp flickering on while riding down the road" Looking at the regulator schematic I can see how a bad ground would do that.


It's interesting that your bike was running rough with a bad ground, I haven't quite figured that out but I had a similar experience when my ignition switch was making bad contact, the bike behaved as you describe, flicking the switch a couple of times seemed to cure it. I talked another guy who's lemans was running hairy into overhauling his switch, he was amazed at the improvement it made.

I haven't quite figured out why the switch contact effected the bike running so much because the ECU gets it's power through a relay, unless it was so bad the relay was dropping out.

I also have a theory that a bad ground can lead to the early demise of the Ducati Energia regulator.

That reminds me, too much voltage at the battery seems to cause the ECU to cut out, making the bike lurch, I think it must have an internal over voltage cut out to protect itself.


It's very easy to check the ignition switch contacts from under the seat.

Test Point Layout August 18 2010.pdf

Measure between the base of fuse 6 to the 30 contact of R3, it should be ~ 0.5 Ohms each time you turn the switch on. The grease inside the switch goes hard after a few years and it holds the contacts apart. Mine dropped from anywhere from 10 - 16 Ohms down to a consistent 0.5 after cleaning.


Raz's point about the injectors is a good one, also if you have a bad connection in the circuit not only does the ECU compensate for the low voltage but also the resistance may prevent the injector opening at all. Each injector is ~17 Ohms so it wants to pull 0.7 Amps

The coils are 0.7 Ohms so they will pull an instantaneous 17 Amps, the fuel pump also pulls a whack of current. From memory the current averages out about 9 Amps but the peaks are easily twice or 3 times that. Any resistance will have a huge impact.


Another thing to check is the state of the relay base contacts, a high resistance there R4, R5 or a bad contact at the fuses can effect the bike's running. Even R2 the headlight relay base will have some effect because that's where the regulators Black wire gets the battery voltage reference from, the same wire also powers the tacho so it playing up can point to a connection problem that may also cause over-charging.


Sorry about raving on here but I love a good electrical mystery. :oldgit:

You don't have to be an electrician to own a Guzzi but it helps.


I'm glad your bike is running much better, I hope others will take note and do this simple ground strap addition.

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KiwiRoy has posted some of the most helpful contributions to our V11's electrical, um, "challenges." His professional approach to problem solving the electrics are second to none.


I really mean it when I say: :notworthy:

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