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09 Stelvio Weak Alternator?

nose2wind

Tuned and Synch'ed
Joined
Aug 14, 2013
Messages
94
Location
Frisco, TX
I was testing my electrical system prior to a long trip.

It is only outputting 13.2 volts. at idle measured at the battery posts. The manual says output should be 14.2-14.8

It also doesn't increase much at revs. Possibly going down at revs.

This seems fishy, can any one confirm what is acceptable?
Checked all grounds etc.

I checked another bike with same meter (Buell) and it registers 14.4
This is my understanding of a correct reading at idle or revs

Specifics:

Resting voltage: 12.8v
idle: 13.18
Revs: 13.18-13.23
 
P.S. I have been riding the bike and have not had the battery run flat...YET...:(
 
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May be the alternator/rectifier, but I would start with the simpler things first. Battery and belt.

Tighten clean all your battery connection. Remove the leads from the battery and give everything a good cleaning and remove all corrosion and then make sure it is tight. Also confirm that the ground lead to the chassis behind the starter is tight.

If that fails, have the battery load tested to see if that is the cause, or if it is more than 3 or 4 years old I would just replace it.

Last thing is has the alternator belt been replaced. May be slipping, although you should hear it squeaking but you never know. You can usually take the inspection plug off at the front (where you turn the crank over for TDC) and see if you can push on the belt or take a look as the ribs. May be time to replace.

Failing all those things, may be time to look at the alternator but I truly don't believe that is the case. Rarely they fail on the Stelvio, but then again, anything is possible.

You do have some charging so does not sound like a blown fuse.
 
How old is the battery?
I tried 2 batteries. Pretty sure that isn't it.
May be the alternator/rectifier, but I would start with the simpler things first. Battery and belt.

Tighten clean all your battery connection. Remove the leads from the battery and give everything a good cleaning and remove all corrosion and then make sure it is tight. Also confirm that the ground lead to the chassis behind the starter is tight.

If that fails, have the battery load tested to see if that is the cause, or if it is more than 3 or 4 years old I would just replace it.

Last thing is has the alternator belt been replaced. May be slipping, although you should hear it squeaking but you never know. You can usually take the inspection plug off at the front (where you turn the crank over for TDC) and see if you can push on the belt or take a look as the ribs. May be time to replace.

Failing all those things, may be time to look at the alternator but I truly don't believe that is the case. Rarely they fail on the Stelvio, but then again, anything is possible.

You do have some charging so does not sound like a blown fuse.
I was testing my electrical system prior to a long trip.

It is only outputting 13.2 volts. at idle measured at the battery posts. The manual says output should be 14.2-14.8

It also doesn't increase much at revs. Possibly going down at revs.

This seems fishy, can any one confirm what is acceptable?
Checked all grounds etc.

I checked another bike with same meter (Buell) and it registers 14.4
This is my understanding of a correct reading at idle or revs

Specifics:

Resting voltage: 12.8v
idle: 13.18
Revs: 13.18-13.23

Checked belt and it looks to be in very good shape. I tried pulling on it and didn't slip at all. about 1/4-1/2" deflection. Talked to Curtis at Harpers and a few others and they think it is fine. Maybe on the low end, but still doing the job. They also stated that these alternators hold up very well. Think I will ride it some more and keep an eye on it. I remember letting the battery run down, due to the parasitic load and barley started the bike. After riding a short while it was stronger than ever. That is not a symptom of a weak charge.
 
Maybe I was being a little paranoid. Guzzi's can have that effect on you! :wasntme:

What readings are you other Stelvio riders getting at idle?
 
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Maybe I was being a little paranoid. Guzzi's can have that effect on you! :wasntme:

What readings are you other Stelvio riders getting at idle?

Bike off= 12.6 to 12.8
Idle= 13.6 to 13.8
Cruise= 14.1

R u running any heated gear. Just running my grips drops the cruise to 13.2 to 13.6 depending on the setting.
 
Maybe I was being a little paranoid. Guzzi's can have that effect on you! :wasntme:
Bike off= 12.6 to 12.8
Idle= 13.6 to 13.8
Cruise= 14.1

R u running any heated gear. Just running my grips drops the cruise to 13.2 to 13.6 depending on the setting.

Thanks, that's helpful. So you are reading 13.6 at idle. Higher than mine, but not by much. I thought mine should have been reading 14's at idle. My Buell reads 14.4 at idle. Mine does not go up much when accelerating as yours did to 14.1. I did a reading with heated grips at full on and that pulled it down by .10v What rpm do you consider cruise? I'm still a little concerned.
 
You tried 2 old worn out batteries? Never said how old there are.

One is a Shorai Lithium recently shipped to me under warranty. We thought the battery might be bad because it was running down. It was the parasitic load that was the issue. That is what started me checking the voltage. The Lithium battery's read a little different that Lead acid, so I decided to swap them out just to eliminate that as a possible issue. For example: The Shorai will read higher at rest

Shorai:

Resting 13.3
Idle 13.4
2,000 rpm 13.5

I never hit 14's at any rpm while testing the Stelvio
 
Thanks, that's helpful. So you are reading 13.6 at idle. Higher than mine, but not by much. I thought mine should have been reading 14's at idle. My Buell reads 14.4 at idle. Mine does not go up much when accelerating as yours did to 14.1. I did a reading with heated grips at full on and that pulled it down by .10v What rpm do you consider cruise? I'm still a little concerned.

That reading for cruise is around 3500 RPM. Does not change much even when I cruise at 4000.
 
Check the batteries in your multimeter and hopefully it's not one of those $5 Harbor Freight ones! I always have 2 digital multimeters for this exact reason. Once when I was getting unusual readings, I tried the other meter and things were reading just fine. Changed the batteries and whammy, the first meter was reading the same as the 2nd!
 
I was testing my electrical system prior to a long trip.

It is only outputting 13.2 volts. at idle measured at the battery posts. The manual says output should be 14.2-14.8

It also doesn't increase much at revs. Possibly going down at revs.

This seems fishy, can any one confirm what is acceptable?
Checked all grounds etc.

I checked another bike with same meter (Buell) and it registers 14.4
This is my understanding of a correct reading at idle or revs

Specifics:

Resting voltage: 12.8v
idle: 13.18
Revs: 13.18-13.23
On my Stelvio I read the same voltages in the display, but with the multimeter directly on the battery i read 13,8 V. I have change the battery 6 months ago but every day she starts without problems.
My mistake was buy a low cost battery(in Italy the yuasa costs from 130 to 160 euro, i spent 50 euro for a Magneti Marelli)....
 
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