Tach wiring need help!
 

Im wiring in a new Autometer tachometer to my 1985 Dodge D100 318 and I have the coil wire and ground wire done, it says in the instructions to hook white wire to 12V dash lighting and the red wire to 12V dash ignition switch. How am I suppose to know which wires are the dash lighting and ignition switch? Im sure plenty of people have done this so any help would be great thanks.

get a test light or ohm meter set on volts so you know what wires are hot {got power} when the key is off and on and to check the headlight switch. Take the headlight switch out with the connector and check which wire is hot when the parking lights come on and doesn't have power when their off. wire your white wire to that one so the tach light comes on with the park lights. You can wire the red one up to any wire that has 12 volts only when the key is on. Check the wires at the bottom of the steering column. and see which ones are hot when the key is turned on and no power with it off. wire it to one of them or any other wire that has 12 volts when the key is on only. I hope this helps. good luck