electronic problem left hand signal light and horn

For some reason my left hand signal light and horn have stopped working. I have checked the fuse and taken apart the signal switch and horn switch and have run a test on them and they seem to be working. It appears that they use a common lead for power. I have taken it to the local bike shop Valley Yamaha but they were unable to assist. Any suggestions.
Scott

If the rear signal on the same side works, I would check to see if the signal and horn share a common ground and check that. Run a separate wire to a good ground as a quick test.
Chris

Neither front or back light come on with the signal switch but all four come on with the 4 way flasher Button is pushed. There is a common wire that both switches when engaged use, Would this be the common ground? Or would it be the positive?