I'm hoping someone on this forum can help me out as I'm not very good with wiring or hardware components (more of a software kinda guy). I'm wiring in some new gauges into my car and need a little help dimming the lights on the gauges. The gauge has 1 wire (which requires a +12v source) to adjust the brightness of the lights. However the car's factory dimmer/rheostat has 3 wires (+12V into the rheostat, ground into the rheostat, and ground out of the rheostat). The rheostat dims the lights by increasing the resistance to current ground coming out of it. I'd like to be able to dim the new gauges using the factory rheostat (which also dims other lights in the car). But as you read above, the factory rheostat effects only the ground, not a positive wire that the new gauges use for dimming. So my question is, is there a way with some sort of electrical component, to take the ground that is coming out of the rheostat as an input, an output a + source that is in proportion to the resistance on the ground wire?