The wiring to the front and rear side to side splits in the turn signal switch. Just because some of the lights works doesn't mean the switch is good. Everything is interconnected in the turn signal switch. I have fixed plenty of these kinds of problems with a new turn signal switch CAM available at most parts stores. Be sure to read and follow the instructions to the letter because you will need to trim the wire whiskers on the new cam exactly like the original ones.
http://www.oreillyauto.com/site/c/search...&vi=1082124
