The gauges in my 1979 Z/28 are inaccurate. The volt meter is down at 8 volts most of the time, the temp gauge stays in the low 100s, the fuel gauge fluctuates back and forth, the speedometer works for a few miles then goes back to zero, and the dash lights only work half of the time. Would the circuit board on the back side of the gauge cluster be the culprit? How can I trace down the problem? I also want to mention that sometimes, not often, everything works as expected.