I just bought a 1987 GMC suburban 350 4x4 automatic as a project truck but the instrument panel dosen't work the lights come on but the gauges don't work. the spoeedometer and odometer do nothing, while the others sometimes float, but mainly do nothin, i checked fuses and grounds and every thing looked ok.i also checked the wheel speed sonsor and it was fine. someone in the past has put a rather expensive stereo system in it and removed the amplifier would have something to do with it?