I have a 1992 GMC Half ton. I have developed a problem with my Turn signals and dashlights. First with the lights Shut off, When I put the turn signal either to the left or the right the turn Signals work but the dashlights flash on and off and the guages bounce as the signal Flashes.

With the lights on when I put the turn signal to the left the indicator on the dash comes on solid and the left signal lights dont work.

I have no clue where to start looking.

it could be that there is a poor grounding or loose connection - this is the most common problem why turn signal lights (http://www.innerauto.com/Auto_Part/Turn_Signal_Light/) won't work. check also the fuses. burned bulb may also cause this problem.