I have been having some issues with my 2004 Sportster 1200C. The right front and rear turn signals will not flash and the break light will not flash (when using the front or rear break). All the lights will turn on though. I changed all the bulbs and that didn't work. The hazards work only for the left side. None of the fuses are broken or dirty.
When I was replacing my handgrips I was able to get the flasher to work for a second or two. Besides that ive had no luck. I think it might be a loose wire or pinched but I haven't seen anything that would indicate that. If anyone has any suggestions that would be great. Thank you.

 

Take a meter and start checking your wiring. You can start by seeing if the brake light and the problem turn signals get 12V at their sockets when they're supposed to be lighting up. I'm guessing that they don't. Then just work your way along the circuits to find where, if anywhere, they're not getting power.

Since you changed handgrips, you may want to check there first with a meter.

 

The issue was happening before I changed out the handgrips

 

Check the wires under the seat, where it clamps in, my Nightster seat had moved and crimped some wires there causing the turn signals to go wonky and in my case, blow a fuse.