Dunno where the brake light switch of ST is located, but on a Dyna its a real goob catcher. Mine was so badly corroded that I had to remove it. I'm using a banjo bolt (thats what we call them here btw) with an internal switch in the rear caliper now.
(also to clear the path for a rear stabilizer in the future)

Something like this:

 

Rear switch is down on the lower frame, follow the rear brake line back from the rotor. You'll find it. It'a a pressure switch.
The pressure from the brake fluid pushes on the switch turning it on. The fluid NEVER enters the switch.
It's on or off, so your switch probably is internally compromised or has corrosion or water in the switch stopping the contacts from touching.
Remove the 2 wires and jump them out to see if the light illuminates to full illumination.

 

But he's got brakes, so he has pressure. It's a pressure switch. The switch is bad.

 

While I'm definitely glad the I flushed the rear brake fluid. It was in fact the switch. Thank you all for your input.

 

cool.. Glad to hear.. Brakes are a good thing...

 

........ and you also flushed the front brake while you were at it?

 

Nice one buddy. Thanks for posting the solution.