screwy signal light

[90dakota]

ok try to follow me all signal lights work without my lights on. with
the lights on, all signal lights work except I have to flick the right
one manually on and off. But here's where it gets confusing when
the lights are on and the brakes are applied I get nothing on my rear
right side not even a break light. I have replaced all the bulbs, I
think it is something in my wire harness but I have fiddled around
with and found anything yet.

90 dakota 3.9L