While driving my 95 blazer, I notice my tach and speedo gauges are moving all around. When I shut the key off, my tach says 1000 rpm and my oil pressure is at 40 psi. When I tap on them they go to zero. Could this be a bad ground or faulty cluster. I know the digital ones had troubles but I am not familiar with analog gauges. Can you help me with this issue? Thanks. Timboboliscious