Please help. Started up the tahoe and everything was working fine. A few seconds passed by and then the message center went totally blank and the gear selector on the instrument panel (P, R, N, D, 3, 2, 1) is so dim that we can hardly see it. Everything else works normal in the instrument panel (spedo, pressure gauges, etc). The manual dimmer switch for the entire instrument panel is set as high as it will go before turning on the dome light. Any ideas are greatly appreciated!