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My 1975 GL1000 Voltage fluctuates.
My voltage at idle is 12.6 volts.
My voltage when riding at 3/4000 rpm on a 40-60 mile ride for the most part is 13.8-14.0 volts.
Sometimes when first starting or on a 40-60 mile ride, the voltage will go to 16.0-17.0 volts for 15-20 seconds
then come back down or maybe will not even do it at all!
The manual shows some 1975's had a separate regulator!
I don't see one!
I too took some pics this morning.
I'm sure that the rectifier/regulator is the problem.
I looked at the Rick's Motorsport website this morning.
They list 2 rectifier/regulators.
1 is just a normal one & the other one is a what they call a Hot Shot Version.
Has anyone used 1 of these?
comments welcome!

Idle charging generally is just adequate to keep the battery up. There really is no surplus at idle, so 12.6 is acceptable. Once you get the rpm up they the Stator will start putting out a significant amount of power. The high voltage (16-17) is a concern. If it stays that high for any length of time you will damage your battery. First thing to check is the ground of the regulator. If the ground is not clean any resistance will result in over charging. You really do not want to see much more than about 14.5.

The 78/79 system is a bit different but on mine I ended up running a hot line through a relay into the "Sense" of the regulator. I was seeing as much as a full volt of drop between the battery reading and the "Sense" wire going into the regulator, and that was causing mine to overcharge.

Also Check out the similar topics below.

My 76 constantly would see the 16-17v when running and as Steve said it ate batteries, usually boiling them out. The solution for me was a Ricks MOSFET regulator/rectifier, now stays at 13.2v consistently ,,, expensive but worth every penny imho. The last battery I replaced since replacing things was 10-12yrs old… I’m happy with that.

Some have fit a later model regulator/rectifier like from a CBR600/CBR900/1000 and have good results but I prefer the straight plug & play from Rick’s plus their support is exemplary.

As Steve above,, an afternoon spent going over and cleaning the grounds is highly recommended,, a few adult beverages helps this as well.

Almost all bikes until electronic ignition was developed had crude regulation, and replacing boiled batteries every year or two was a thing we just lived with. It just wasn't a priority. When I had a Suzuki GS1100, there was a whole website dedicated to helping people get their charging systems running properly. Called "The Stator Papers", or something like that.

I don’t have a boiling battery issue!
Where does the regulator ground too, ground location at the headstock?
Yeah, I looked at the Rick’s ones.

Extreme system voltage issues may also negatively affect an, electronic ignition system.
Around 10 years ago I had spoken on the telephone with a technician at Dynatek when I had a problem with one of their 3 ohm ignition coils. (The lowest of its double outlet sockets was "dead",)
During that conversation I was suddenly curious if overvoltage ( the dreaded 17 volts ) scenarios might be attributed to their ignition coil failures. Hmmmm?
He then puzzled it might be a reasonable concern based upon the fact they dynamically tested their 3ohm ignition coil design at a maximum of 16vdc.

Silly question: How are you measuring the voltage and have you verified that the meter used is accurate?

Note that it is normal for the alternator's output to vary depending on engine RPM (IIRC you need something like 2800 RPM before there is enough to actually charge the battery) and that the FSM specifies that the voltage should be be between 14 and 15 volts when the engine is turning fast enough to charge (I think they specify something like 4000 RPM).

16-17V sounds like a lot but it is only about 14% high. Running at that high a voltage all the time would "boil" the battery but I don't think 20 seconds of that would hurt the battery much.
I think you may be on the right track about the ground connection. As with almost everything else on the bike the regulator connects to ground via a green wire in the bike's harness.

Shadowjack: I used to have a couple of GS400s and I remember the "Stator Papers" well, particularly that there were a couple of glaring errors that I told them about but they wouldn't correct. That was one of the reasons I didn't stay on that forum long.

I have measured it with 2 meters.
I run a digital meter on the bike (see picture)
Like I said, 90% of the time it’s running 13.8 - 14.0 volts then out of nowhere it spikes to 16-17 volts for 15-20 seconds, then back to 13.8-14.0 volts
It’s like the regulator sticks.

This may not be an answer to your situation. BlueThunder had an aftermarket Rectifier/Regulator assembly always overcharging the battery.
He couldn't get a straight answer from the vendor but we finally figured out how to make the original GL1000 charging system components operate as intended.
https://ngwclub.com/forum/viewtopic.php ... 10#p674010

Whiskerfish wrote: ↑Thu Apr 17, 2025 8:16 pm Idle charging generally is just adequate to keep the battery up. There really is no surplus at idle, so 12.6 is acceptable. Once you get the rpm up they the Stator will start putting out a significant amount of power. The high voltage (16-17) is a concern. If it stays that high for any length of time you will damage your battery. First thing to check is the ground of the regulator. If the ground is not clean any resistance will result in over charging. You really do not want to see much more than about 14.5.

The 78/79 system is a bit different but on mine I ended up running a hot line through a relay into the "Sense" of the regulator. I was seeing as much as a full volt of drop between the battery reading and the "Sense" wire going into the regulator, and that was causing mine to overcharge.

Also Check out the similar topics below.

Where is the Rectifier ground located?
So I am looking at the wiring diagram & also the shop manual.
The manual doesn't even list where the main grounds are?
I only know the one by the steering head, other than specific grounds like the switches, fuel meter, etc!

dartman1962 wrote: ↑Thu Apr 17, 2025 3:11 pm My 1975 GL1000 Voltage fluctuates.

The manual shows some 1975's had a separate regulator! *All * 1975-79 GL1000s came with a REGulator Assembly mounted on the left side of the shelter frame.

I don't see one! *It used to be positioned over the large diameter hole that the left side of the air filter housing is visible through; above the reddish-brown diodes.

**A separate RECTifier Assembly is positioned on the front vertical surface of the battery frame...above the ignition condenser.

"I'm sure that the rectifier/regulator is the problem." Time's a wasting to be rid of it

I looked at the Rick's Motorsport website this morning.
Has anyone used 1 of these?

comments welcome!


IMG_5019.jpgIMG_5022.jpg

Here's a Very good group discussion re: new Rectifier/Regulator assemblies purchased from well known aftermarket vendors

https://ngwclub.com/forum/viewtopic.php?t=78165

Cliff, you beat me to it!
It came down to making sure the regulator is properly grounded.

dartman1962 wrote: ↑Fri Apr 18, 2025 12:45 pm

Where is the Rectifier ground located? SNIP

Most everything is grounded through the frame, including the rectifier. The main ground is sandwiched between the triangle engine hanger on the left side of the bike and the engine. Yes it is safe to remove just that one engine support to clean the ground. When putting it back on just get the 2 frame bolt started a turn or 2 before installing the long cross bolt other wise it can jam up.

If you have a decent ohm meter you can with the bike off you can measure resistance between the neg terminal on the battery and the various places on the bike. Anything above about a .1 or .2 ohm would give me cause to investigate.

That's where the battery is grounded to the frame. The green wire in the harness is connected to the frame elsewhere; It has been a long time since I had the '77 so I don't remember specifically where that is but if you say it is near the steering head I'll believe you.
As I said before, the regulator itself is grounded by its connection to the green wire.

There might be several. Can't remember on a 1000, but at least by the time they developed the 1200 there are two or three ground terminals for the main harness, not just one.