V65 Lario, voltage drop below 12v when lights turned on, otherwise charging ok

[Gray Kay]

Hi all electrical wizards.

My Lario charges ok when riding normally





but the voltage drops below the central mark- below 12v when I turn the head lights on.

I recently fitted a new AGM battery but don't think that would affect this.

Been over the usuals, earths and connections but am missing something.

I have a spare voltage reg but no difference with that fitted.

I read most of the posts regarding charging but none seem to cover this situation.

Any help gratefully accepted, egg on my face just part of the Guzzi learning curve, no probs hahahaha

Cheers from Oz. Gray.

[NevNZ]

I have exactly the same problem with my Le Mans V. In my case the lights, heated grips and radar detector are all run through relays triggered by the standard switch gear wiring, but using a good size power feed straight from the battery. The instrument cluster volt meter shows good charge with everything off, but as soon as I turn the lights on, use the indicators or brakes the voltage drops way below normal. I found an earth wire hanging by a thread in the main connector under the instrument cluster and thought great - there's the problem. Fixed that and sorted out other potential issues by replacing that old 15 connector molex plug but the problem persists.  Took it to the auto electrician a couple of weeks ago and he stuck a volt meter on the battery and couldn’t see any significant voltage drop when the lights and indicators go on. The current  theory is that it’s the volt meter in the instrument cluster, or other associated wiring in that area that’s causing the indication of low voltage, and I can’t be arsed taking all that stuff apart to investigate further. Bottom line – if the battery is getting good charge then the core systems are working no matter what that volt meter says.

Nev

[Chuck in Indiana]

I've decided it's normal.  The Gauge *does* read low, according to my digital volt meter. That said, when mine was reading lower than "normal," I found a fuse that was corroded. Brightened up the fuse holders, put new fuses in, and it made a noticeable difference.

[huub]

the volt meter shows the voltage in the instrument cluster,
if you measure the voltage at the battery you will probably find it charges Ok.
you loose voltage in corroded connectors and fuses.

my lario does the same, after i found out it charges ok despite the low reading, i didn't give it another thought

[Kiwi_Roy]

I've decided it's normal.  The Gauge *does* read low, according to my digital volt meter. That said, when mine was reading lower than "normal," I found a fuse that was corroded. Brightened up the fuse holders, put new fuses in, and it made a noticeable difference.

It's normal for my Lario, I run with my gloves and heated vest on high, never fails to start.
I suspect it's just the way the wirings arranged creates a Voltage drop at the measuring point.

[Howard R]

Simple answer is, the voltmeter is hooked into the wiring harness somewhere near the headlight.  Headlight off, very little current draw, therefore not much voltage drop along the (typically undersized) Italian wiring.  Turn on headlight, many more amps involved, so more voltage drop due to Italian wiring. 

Bottom line, check at the battery with a good external voltmeter.  If voltage looks normal there, take whatever the in-dash meter says as normal operation and keep riding.

Howard

[Arizona Wayne]

This is nothing new on older Guzzis that don't have much watt output until you get the motor up to at least 3,500 rpm. Then you will see your meter where it should be.  That is what the meter is for....to let you know when your voltage is proper to keep your battery from being drained unexpectedly.  Unless you are doing @ least 3,500 rpm you need to turn the heated grips off.    Just pay attention to what your meter tells you. 

[Gray Kay]

Thanks everyone, great support.

I did some DVM testing today, idle shows 12.4v across the battery, up to around 13.5v at 3500 revs with lights off.

and... virtually the same meter readings across the battery with the lights on... at 3500 revs, with the dash meter just into the left.

Maybe it is "just the guzzi way" but showing good charge is the right result.

I would rather see around 14.2 volts but will ride happily with this for now.

Thanks again.

Just wondering if I re-wire the dash voltmeter from nearer the battery...

Thanks again.

Cheers from Oz.

[Chuck in Indiana]

I'd clean and DeOxit all the connections in the charging system..

[tris]

The voltmeter on my 2005 B11 shows it barely /bottom limit charging. When I put a calibrated DVM I borrowed from work across the battery, its actually 0.6V higher

I now just add 0.6V in my head to whatever the dash says

Obviously runs in the MG genes

[chuck peterson]

I found 3/4 volt by running a second ground from the diode board to the trans...found a bit with an adjustable reg...found a poor solder at the brushes...two diode boards...new rotor...cracked coil...springs hung up...replaced heat cycled  front wiring loom...cleaned scrapped grounds...bad condensers

Plenty of fun stuff to look for.... phuuuutzzz....zap.. ....zot....melt.

I think the  reputation of Italian motorcycle electrics comes from them lasting for 30 years...something's going to give.

[Chuck in Indiana]

I think the  reputation of Italian motorcycle electrics comes from them lasting for 30 years...something's going to give.

Right. I've said before, If you look for trouble in an old machine.. you *will* find it. 
Fix it in the comfort of your shop before it becomes a problem in BF Utah..

[huub]

Thanks everyone, great support.

I did some DVM testing today, idle shows 12.4v across the battery, up to around 13.5v at 3500 revs with lights off.

and... virtually the same meter readings across the battery with the lights on... at 3500 revs, with the dash meter just into the left.

Maybe it is "just the guzzi way" but showing good charge is the right result.

I would rather see around 14.2 volts but will ride happily with this for now.

Thanks again.

Just wondering if I re-wire the dash voltmeter from nearer the battery...

Thanks again.

Cheers from Oz.

the original regulator of the lario is adjustable , so if you want 14.2 volt at 3500 RPM you only need to adjust it.
obviously you need to measure the voltage at the battery if you are setting the regulator

[chuck peterson]

14.2 volts....You also want to remember if that is headlight on or off...I crept up to a lotta voltage slowly, checking the battery for too much heat after hi way runs...it's nice to know you can fully charge the battery with the headlight off without melting the battery/charging system...this was pretty critical to watch with my convert with no jump starting