Generator or Voltage Regulator

[TheBru]

1973 CHP ElDorado. Oddly enough my Guzzi wouldn't start. I jumped it from the car and it started right up. However at idle I'm only reading ~9.5 volts, with throttle ~14.5 at the battery. It needs a new battery but I'm also leaning towards a new voltage regulator. It is the original. If the generator was bad I wouldn't think it would put out 14.5 at anytime. Any thoughts??

[Tom H]

How old is the battery? Reads like you might need a new one. Then check charging voltage again. 14.5V when reved out of on old gen is pretty normal to me.

Tom

[Wayne Orwig]

If the battery has been sitting for a long while uncharged, it is easily sulfated and ruined. Try a GOOD charger on it to see if it comes back.

Is the headlight on? The generator can't do much at idle with the headlight on. Higher revs and 14.5V is much as expected.

I would plan on a new battery, and keep it charged properly. Don't idle it much.

[TheBru]

The battery was bought 09/04/2020. I plan on replacing it possibly today. I don't ride it too much anymore which I know is bad for a battery. I still don't understand why that would cause a reading of only ~9.5 volts at idle at the battery cables. Even at idle shouldn't I still be getting 14.5?

[TheBru]

If the battery has been sitting for a long while uncharged, it is easily sulfated and ruined. Try a GOOD charger on it to see if it comes back.

Is the headlight on? The generator can't do much at idle with the headlight on. Higher revs and 14.5V is much as expected.

I would plan on a new battery, and keep it charged properly. Don't idle it much.

It shuts down my charger after a bit. The lights were off. I turned on a blinker at idle and it didn't work until I revved it. Same with all the other lights. I am going to get a battery. The drop in voltage at idle, even with a bad battery just seems strange.

[Tom H]

If the battery has a bad cell, that would cause it to be 9.5.

A Gen "generally" will not charge at idle. I do not recall the exact revs before it starts charging, 1000-1500rpm? An alternator will "generally" charge at idle, at least once it's reved enough to start charging. This all depends a bit on the alternator.

Tom

[TheBru]

If the battery has a bad cell, that would cause it to be 9.5.

A Gen "generally" will not charge at idle. I do not recall the exact revs before it starts charging, 1000-1500rpm? An alternator will "generally" charge at idle, at least once it's reved enough to start charging. This all depends a bit on the alternator.

Tom

Guess I'm still not understanding why the battery would effect the generator output while running. I am testing it at the battery cables while running.

[guzzisteve]

You are thinking correctly, get a new batt first. What AH is batt? I use all 34AH in my V700 and the other Tonti's .

[pehayes]

You aren't listening to the advice.  The generator sounds just fine if it jacks to 14.5 at higher rpm.  The battery won't store the excess so the battery is faulty.  When rpm's drop to 1500 the generator barely puts out anything above base battery. When rpms drop below 1000 its probably a deficit situation and  you are now in a 'drain' situation.  You are no longer reading the generator.  Now you are reading just the base battery.  Hence the low number.  Once running, that low voltage is probably still enough to generate spark and keep the motor at idle.  But you could never crank start with that low battery voltage.

BTW, if you haven't bought a new battery as yet, stay away from traditional flooded cell batteries.  They don't last. Especially under long storage.  You'd get higher voltage and much better longevity from a good AGM class battery.  Also, the flooded cell batteries eventually leak and corrode switches and wires around on the bike.

Patrick Hayes
Fremont CA

[TheBru]

You aren't listening to the advice.  The generator sounds just fine if it jacks to 14.5 at higher rpm.  The battery won't store the excess so the battery is faulty.  When rpm's drop to 1500 the generator barely puts out anything above base battery. When rpms drop below 1000 its probably a deficit situation and  you are now in a 'drain' situation.  You are no longer reading the generator.  Now you are reading just the base battery.  Hence the low number.  Once running, that low voltage is probably still enough to generate spark and keep the motor at idle.  But you could never crank start with that low battery voltage.

BTW, if you haven't bought a new battery as yet, stay away from traditional flooded cell batteries.  They don't last. Especially under long storage.  You'd get higher voltage and much better longevity from a good AGM class battery.  Also, the flooded cell batteries eventually leak and corrode switches and wires around on the bike.

Patrick Hayes
Fremont CA

Not sure what advice I wasn't listening to but your explanation does make a bit of sense. Just never seen it happen that way. I went looking for a battery today.  I had a Group Size 58 in there but would like to find something a bit smaller without breaking the bank on it. Considering a tractor battery. Seems several people have used them with good results.

[John A]

The very first thing on any charging system troubleshooting literature is ensure you have a good battery before you start. Otherwise you are wasting your time because any reading you get will be skewed depending on battery condition

[jrt]

I will reiterate what Pat said-  you aren't reading what you don't want to hear.  Get a good AGM battery and don't waste money on a lawn tractor battery.  I know a lot of folks run them, but they won't last, especially if the bike sits for extended periods. 

[Antietam Classic Cycle]

Not sure what advice I wasn't listening to but your explanation does make a bit of sense. Just never seen it happen that way. I went looking for a battery today.  I had a Group Size 58 in there but would like to find something a bit smaller without breaking the bank on it. Considering a tractor battery. Seems several people have used them with good results.

A garden tractor battery with high cranking amps and sealed construction will cost as nearly as much as this AGM battery. I've used this in a number of customer Guzzis, as well as my own. https://www.amazon.com/gp/product/B00B9JD7PG

[TheBru]

I will reiterate what Pat said-  you aren't reading what you don't want to hear.  Get a good AGM battery and don't waste money on a lawn tractor battery.  I know a lot of folks run them, but they won't last, especially if the bike sits for extended periods.

What was it I didn't want to hear?

[Kev m]

What was it I didn't want to hear?

That 9.5V at idle does NOT necessarily indicate a bad Gen because you are likely reading battery voltage at that point.

Or stated another way that you must first replace the battery with a known good and recheck, but the 14.5 V at speed suggests both a properly operating Gen and regulator.

[TheBru]

That 9.5V at idle does NOT necessarily indicate a bad Gen because you are likely reading battery voltage at that point.

Or stated another way that you must first replace the battery with a known good and recheck, but the 14.5 V at speed suggests both a properly operating Gen and regulator.

I did want to hear the Gen was probably good. Why would I want to hear otherwise? And I stated from the first post, and several times after, I needed a new battery and even went put looking for one.

[Wayne Orwig]

Guess I'm still not understanding why the battery would effect the generator output while running. I am testing it at the battery cables while running.

Normal generator output at idle often can't keep up. The system is running off of the battery at idle and the generator needs some revs to start producing enough to run the bike. And a few more revs to even charge the battery. 

[Kev m]

I did want to hear the Gen was probably good. Why would I want to hear otherwise? And I stated from the first post, and several times after, I needed a new battery and even went put looking for one.

See your own replies #'s 3, 4, and 6.

That's what people are referencing.

[AJ Huff]

It's threads like this why I've stopped asking for help.

-AJ

[Kev m]

It's threads like this why I've stopped asking for help.

-AJ

Why? He asked for clarification - so he's getting it.

It sounds like it's just miscommunication. Which isn't anything for any of us to get our feathers ruffled about.

I don't think anyone is being angry or insulting.

Do you?

[Frenchfrog]

Agreed kev M ! He's had excellent and prompt  advice and from extremely knowledgeable people to boot.You can either listen to that or learn the hard and expensive way.