Yes you can adjust the brightness of lighted gauges. First you need to know if the lights are LED or filament type. Most likely filament type but these days LEDs are everywhere. You can install a switch so you can install a mere resister inline and when you want a bright gauge lights, you can short out the resister, and if you want the gauge lights dimmer, you can switch the resister in. Kind of how your vehicle gauges work. So you need to know how much current your gauges draw. If you have a meter with a current option, you can see how much current the gauge lights draw. Then selected a resister to dim them to where you want them to be and install a resister to set that level. But make sure you use the proper wattage resister also. I know this sound complicate but in reality easier then you would think. Another option is to install a diode inline. As you install a diode, the voltage drops by about .6 volts. So it may take two or more to get to where you want the level. Just make sure you install the diodes in the right direction. You will know if you install it wrong, because no lights will light. So simply switch it around. And keep adding diodes until you get what you want... A good diode is a 1N5400 series (1N5400, 1N5401,etc.). They will handle 3 amps. I can't see your lights needing more current then that. And if the current is less then an amp, you can find 1N4000 series diodes will work perfectly. Easy Peasy... JMHO!