Volt meter 1980 1000SP

[snobear]

My volt meter on the 1000SP reads fine when the headlight is off but with the headlight on it shows virtually no charging.
I assume there is a better way to wire this unit and am looking for some suggestions.
I have no issues with charging it is just the meter that is wonky.

[guzzisteve]

The one on the Cal2 works better than the one on my old SP but it's still a little wonky. I run w/headlite off after starting and off at stop lite
I call it overly sensitive.

[Wayne Orwig]

Add a headlight relay kit from Eastern Beaver. It will move the headlight load directly to the battery. That should help unload the wiring a lot, plus you get a brighter headlight.

BTW, the low voltage may be telling you that you have a poor connection that may need looked at.

[Kiwi_Roy]

What sort of Voltmeter is it, not an old school Analog?
I have put cheap digital Voltmeters on several Guzzi's, I wire them across the city Light bulb
I start out about 12.5 and range up to 14 at 4,000revs
http://www.thisoldtractor.com/guzzi007/schematics/1978_V1000_SP.gif
The Voltmeter is fed from switched fuse F3
It won't charge as much with the headlight On, a typical Incandescent would draw  Amps

[guzzisteve]

 Roy, They are analog on older Guzzi's if you didn't ride one. THEY are GREAT, no electro crap you don't need.
Wayne has the right idea & make it sweep less when you turn lites on & off. My volt meter reads at just under 14V then drops at idle.

[Wayne Orwig]

What sort of Voltmeter is it, not an old school Analog?
I have put cheap digital Voltmeters on several Guzzi's, I wire them across the city Light bulb
I start out about 12.5 and range up to 14 at 4,000revs

I assume the old school mechanical dial.

[guzzista]

I have mine directly routed from battery,+ ground activated  on key on circuit. And of course , as Mr Wayne suggested ,  relays for headlight  ( in my case both on low and high beam supply)

[snobear]

Thanks for the suggestions, sounds like the relays for hi and low beam are the way to go.  Better lighting and load off the switch wiring all makes good sense.
The system is charging fine it is just the volt meter that struggles.

[snobear]

This probably explains something else I was struggling with.  I was always leaving the headlight on and occasionly the starter relay would not transfer enough volts to trigger the stater solenoid unless the headlight was off.  I replaced the starter relay as well so now I have a few spares that will work for the headlight hi/lo

[moto]

It sounds to me like your voltmeter is fine. It is just telling you something you don't like about the state of charge when you have the headlight on. It is easy to make a test voltmeter that you can clamp to your handlebar and wire directly to your battery terminals, if you'd like a second opinion. Here's the one I made from a cheap voltmeter and a broom handle bracket:







You put it on the handlebar and plug it into the battery charging cable, then ride around and see what's up.

[Wayne Orwig]

This probably explains something else I was struggling with.  I was always leaving the headlight on and occasionly the starter relay would not transfer enough volts to trigger the stater solenoid unless the headlight was off.  I replaced the starter relay as well so now I have a few spares that will work for the headlight hi/lo

If you do it right, you can 'ground' the headlight relays through the starter motor. The low current for the relay will of course not spin the starter, yet when the starter button is pressed the relay will drop out and turn off the headlight, which may fix that issue if done right.

[jhem68]

Add a relay at the voltmeter powered off the + and - coming from the input currently powering the voltmeter. Then run power coming out of the relay directly from the battery + (through a fuse) to the voltmeter. Ground the voltmeter to any convenient ground. I think you will find that Wayne in reply #2 has the voltmeter problem nailed down.

I assume the charge light is operating correctly and the voltmeter is not showing a voltage drop at the battery with the lights on but rather a voltage drop at the voltmeter with the lights.
You can ziptie the relay to the fairing strut right next to the voltmeter. That's what I did on my 1980 SP when I encountered the same problem.

The starter interruptus mod is probably a good idea for your start issue.

John H

[steven c]

 It just annoys me that the two 79 SP's I had had a voltage gauge but my 2020 V85TT with it's electronic info display does not.

[Kiwi_Roy]

My volt meter on the 1000SP reads fine when the headlight is off but with the headlight on it shows virtually no charging.
I assume there is a better way to wire this unit and am looking for some suggestions.
I have no issues with charging it is just the meter that is wonky.

It's ok to not show a charge, if it indicates 12 Volts at mid revs that's all you can expect, it might drop below 12 at idle that's ok provided it comes back above 12 at ~3,000
Update:
http://www.thisoldtractor.com/guzzi007/schematics/1978_V1000_SP.gif
You can see its connected to the switched fuse F3
If you have a multimeter measure the Voltage between battery Positive and fuse F3, maybe you have a dirty ignition switch dropping Voltage, should be < 0.2 Volts drop.
The schematic shows a 45 Watt main beam, that's 3.75 Amps
You might try an LED headlamp, that will draw less.
https://www.amazon.ca/Headlight-Motorcycle-Headlights-30SMD-Chips/dp/B09Y8WQD62/ref=asc_df_B09Y8WQD62?mcid=0fa1a088017836e2a5021d315428e16b&tag=googleshopc0c-20&linkCode=df0&hvadid=706745692759&hvpos=&hvnetw=g&hvrand=15908524821205784327&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001500&hvtargid=pla-2299423691468&gad_source=1&th=1