Look on your wiring diagram and look for a common point for all the malfunctioning circuits, usually they will have a common supply point or a common ground. That's where you look.

 

It looks like the oil & neutral lights, brake light, horn, & turn signals are all feed from the ACC breaker. I think that the oil light grounds thru the oil switch (sender unit), the neutral light thru the neutral light switch, the horn thru a ground wire to the frame, the brake thru the bulb socket, and the turn signals thru the bulb sockets.

 

Lets start with the first problem. The rear brake light. You said if you push hard it will come on but not on a light application. That would not be a ground issue. I know for a fact that when the brake fluid is contaminated (moisture) it will mess with the brake switch. That's exactly what happens to mine so I flush the rear and all is fine again for a few years..

 

I looked at the wiring diagram in the service manual. This is going to take a magnifying glass and some study.

 

Take the wiring diagram to FedEx Office and enlarge it on one of their copiers. I've found it's a lot easier, you can make several copies, and use a colored felt tip to trace circuits.

Basically how I figured out installing the OEM electronic cruise control on my FLHS.

 

Try here: https://serviceinfo.harley-davidson....cle/lookupForm


If the link works for you, then you should be able to get wiring diagrams for your bike. The nice thing about seeing them on the computer is that you can zoom in on sections of the diagram to make viewing easier.


Above is an example of the diagram for your bike enlarged.