I have a 1990 chevy crew cab. when i put either turn signal on, all the lights in the front flash together (side markers and the ones below the headlights). Both turn signal lights in the dash blink as well. The rear lights however function properly as if nothing was wrong. I have cleaned up both grounds on the core support. all 4 lights blink full strength. any ideas on what could be the problem? truck has a western hauler conversion on it if that changed anything.