Welcome back Rufus

 

As stated in the first post, my reg and stator passed all the tests, done as instructed in the stickies .
but, I'll go through it again
1990 ultra.
New regulator and stator. Since i know someone will ask, I replaced these items because the stator wires grounded themselves out in the case, and burned up the connectors.
my battery is good. I load tested it with my own load tester.
again...the battery is good. It's been load tested, and passes with flthe flyingest of colors.

No extra lights.
I have a service manual.
when i replaced the stator, I didn't use an impact.
I don't trust the oe volt gauge. Any voltage readings I post, are taken at the battery using a Klein digital vm.

My bulb sockets are clean. New bulbs, with a very light touch of dielectric grease.

I'll check the brake switch for the rear brake, that could be a possibility.

The vr/stator are cheapy vtwin parts, cause that's what my Indy had in stock, and I needed to get back on the road. But again, I've tested things according to the sticky, and have no problems there, but I'm still curious as to why I have this voltage drop when the brake is applied. Oh...i forgot...when I use my turn signals, the other lights on the bike dim and get bright with each flash. Like a ground issue. But I've cleaned every ground I can find, and replaced a couple ground cables/wires.

I'm doing fork seals this weekend, so I'll have that birdsnest of wires in the fairing exposed, so I'll clean connectors there, maybe that will help some.

 

I'd say you have a wire in the brake light circuit making a partial ground or the loom has been rubbed through somewhere letting all the wires touch, not enough to trip a breaker or fuse but back feeding into the system, hence everything going goofy when hit the brakes.

 

Couple of things - 12.5v riding with brake light and or turn signals on is not bad voltage at all, assuming the OE gauge is in the ballpark. That is, things should work well at that approx. voltage.
If you have a vacuum pump of any kind, or a long rubber hose to hook to a car engine, you really don't have to take the dash and tops of the forks apart most often. Usually get lucky especially if you have an impact to quickly spin the screws out the bottom of the forks. But then, working on electrics you won't be wasting time pulling the speedo and tach dash.
Assuming you don't have self canceling turn signals (?) check your flashers. They have a habit of falling out of the clips and rubbing in weird ways. In Utah once I had one loose and it literally tapped the trees till it knocked the cover off and was shorting everything out. And, I've seen them get water inside and drive you crazy finding those results.
It's been several years ago since I did, but I've wrenched a lot and sometimes it's too easy to relate every scenario one has ever experienced, so forgive me if I've rambled on with too much info.

Remember, everything runs thru the breaker under the seat. Check first for a voltage drop there, with a meter. There are 3 circuits beyond that - ignition, accessory and lights. The accessory circuit runs the radio, brakes, turn signals, gauges. Lights run tail, marker and head lights. Ignition runs only that and the tach.
Have fun - stay dry if you can

 

I did replace the 30a circuit breaker, and made a larger gauge ground for the relay under the seat.
i do have self-cancelling signals, theyre on some sort of timer. It seems to work as it should.
I'm good with too much info...I know I overload my posts with too many details