New owner of a 1988 XJ6 Vanden Plas saloon. The instrument cluster will go dark intermittently, including the gauges on the left side and the odometer. A light tap on the dash will light things back up. The "trouble" panel on the right seems to remain operational at all times. When the left side and odometer is lit all seems to be reading proper temperatures, voltages, mileage, etc.

I am guessing there is a loose electrical connection behind the cluster. Any advice?