Have you recently replaced or reinstalled the batteries? From what you describe, I take it that the gauges power up when 2 is selected but go out when you turn on anything else. There are several possible reasons for this: The connection of the hot or ground cable for battery two is poor. A corroded connector or lose connection will cause the problem you see.
Make sure that the common ground cable connecting the negative terminal of battery 1 to battery 2 is connected and tight.
2: The battery selector switch is bad.
3: One battery is bad. You can check the third possibility by swapping the batteries and se if the problem stays with battery 2 or it moves. If it moves, the battery is bad.
You can check possibilty 1 and 2 by using a voltmeter. Measure the voltage at the fuse block near the console or even at an accessory outlet. It should be 12.5 volts or better with the engine off. Turn something on and see what the voltage is. If it goes very low ( less than 11 volts or so) try the test again measuring the voltage at the #2 battery terminals. The voltage won't go low unless the battery is bad. Now move the voltage measurement to the feed off of the battery switch (This may be a little difficult to get to depending on how it is cabled). Repeat the test measuring the voltage with no accesories on and then after you trun something on. If the voltage at the battery was good with load but the voltage at the common feed of the battery switch is low, the switch is bad or one of the battery cables/connections is bad.
I probably haven't been very clear in my proceedures but if you or a friend has some electrical trouble shooting knowledge, my sugestions probably make sense.
