And this time it isn't the stator/regulator .Did all the tests again, today, and that part is good.
good battery, too. 100% positive.

Here's what's been happening...
I have good voltage when running, with lights on.
when I hit the brake pedal, and the brake lights slowly illuminate, my voltsge drops to less than 12.5v.
so my turn signals don't work when I have the brake applied. Brake off, rev the bike. They work.
I'm having a major voltage drop where, but have no idea where to begin.
I've cleaned all the grounds I can find. Made a new ground cable for the battery. And cleaned any terminals/connectors under the seat. Replaced bulbs with what the book calls for. No real changes.
any ideas?

 

Since nobody else seems to be jumping in....

Does it do this when either brake is applied--front or rear? Or just one of them?

Sounds to me like the wire going back to the brake light is partially shorting, like the insulation has been rubbed off somewhere and it's rubbing on the fender, or frame, or something. Not shorting enough to trip a breaker or blow a fuse, but enough to cause a significant voltage drop.

If you have a voltmeter, I'd try removing the lamp in the taillight and carefully measure (don't short anything when measuring) what the voltage to the brake light does when a helper applies the brakes. As I'm sure you know, the brake lights shouldn't "slowly illuminate". The electrical current that should be going only to the brake light has to be going somewhere else when you hit the brakes.

If I knew the model and year of your bike and could find a wiring diagram for it, maybe that will help us figure this out.

Others with more experience will most likely chime in soon...

Good luck!

 

What is your ac and dc voltage at idle and at 2000 rpm...?

Does it all work ok at 2000 rpm and above?

 

 

Everything works above 2k rpms.
no led bulbs.
I haven't found any bare wires etc

 

Just another angle: While replacing the rear bulb, did you look at the connector (where the bulb contacts the connector)? Sometimes they get a bit corroded causing a larger load than normal (corrosion acts as a resistor). A little sandpaper cleans them right up.

 

if you're looking at the harley volt meter, don't believe it. they are notorious for being inaccurate. take a digital hand held meter and check the power right at the battery. the voltage on your bike meter will be different than the hand held meter. i can guarantee it.

 

Tell us what you are working on...

Any aftermarket electrical parts on the bike?

How did you determine the battery is good?

Are you reading the voltage with a multimeter, or a gage on the bike?

 

The front brake light switch is mechanical, mounted in the right handle bar control assembly. The switch for the rear brake, which is mounted to the master cylinder, is hydraulic. It's just inside the right frame rail between the trans and engine and easy to see from underneath. I have seen them go bad internally causing a "soft" short thru the brake fluid to ground. As often than not, if that one is bad it may be damp, if not outright have a drip of brake fluid on it. (but not always)

So do this; disconnect both wires from the rear brake master cylinder switch and see if it still does it using the front brake lever. If that's good, jump the connectors you unplugged from the rear switch. If that lights up the brake light as it should, then that switch is your problem. DON'T buy a universal brake light switch from an auto parts - they won't last long, trust me I know. Get one from HD, a few more bucks, but it will last.

Let us know what you find

 

As stated we need more info on the charging system. How old are the rotor and stater and what brand.. it so makes a difference!!! Also it's not good to use an impact on the crank nut. An impact produces dead blows and if you read the warning on the rotor it states "no dead blows".... Why, you ask? Dead blows to a magnet will weaken the strength of the magnet and a weaker magnet at lower rpm's will produce less ac voltage... Also 12.5 v at idle when applying the brake is too low, unless that is you have a lot of lights....13v is acceptable at idle. Also did you bring your battery to say like, AutoZone to have it load tested to confirm it will hold under load?