Sportster SE. started cutting out last week.Replaced the controller connections right away.Sounds like its shorting out in the headlight assembly. Known problem? Can I get a wiring Diagram?

Regulator should not affect headlight fuse blowing. You could do a voltage drop test otherwise look for a short circuit in the headlight wiring. IS it shorting and blowing the fuse on both low and high beam? Look for chaffed, broken wireing insulation on wires in headlight assembly and wherever the wires might be crushed by steering stops or mighth be rubbed through from vibration etc.

I suggest check ground connectiosn and look some electrical short, testing cricuit from fuse box.

If it is a 3.8 engine change the crank sensor,they go bad on the 3.8 engines.

You have a short in the start button. Check it out with a multimeter.

There is a wiring harness that feeds to the door, electric door locks and windows draw a lot of amperage. Try removing fuses one at a time that supply power to your door controls until you see the problem go away. If that doesn't work, try other fuses to accessories like interior lights. If your headlights are dimming you have a power wire shorting to another circuit, if it were to ground it would blow a fuse.

Could be something as simple as a vapor lock.

Somewhere you have a dead short, i.e. wire shorted to ground. Only solution is to trace all your wires from the fuse box to the switches, headlight, horn, and turn signals. This will be much easier if you have access to a service manual, but can be done without one if you are patient.

Sounds like a dead short check all the wiring

Turns out the crank sensor needed to be replaced again (second time in 8 weeks or so!). In the last week Harley has sent out a "improved" crank sensor that does not have the issues of the original. Therefore if you replace it once you shouldn't have to do it again and again. Bike runs great now. We will see - though - my local service manager promises it will stay that way.