Newbie question here. I'm hardwiring a Whistler XTR-580 to the rear view mirror plug with a product similar to an Iniviscord. I need to tap into the 12 volt switched power supply but I'm not sure which one is correct. I don't have a voltmeter. But the pin-out is as follows; Brown - Ignition 3 voltage, Black - ground, Lt. Green - Back up lamp supply voltage, Grey - Interior lamp control, Dark Blue/White - Courtesy lamp supply voltage. I know my ground wire pin goes to black, but which of these is the ignition voltage? My guess would be brown, but I'm uncertain what "Ignition 3 voltage" means. Of course, the pin-out doesn't call out the voltage on each wire or get more specific than above. Thanks for your help. 2004 Impala LS with dual map lights on RVM.