Gauge Installation on a Dodge 6.7L Cummins

For connecting the gauge illumination source you will need to access the rear of the factory headlamp/dimmer switch. This is a picture of the headlamp switch connector after it's been disconnected. On this 2008 model, the illumination wire is Orange with a Brown Trace. It is located on the top row of the headlamp switch connector.  There may be more than one wire with the same color. You must test the wires first to be sure which one to connect to.  Connect the plug back into the headlamp switch assembly and test the wires with a voltmeter or test light to identify the correct one.  Turn your parking lights on.  With the test light you should see the light get brighter and dim with the adjustment of the dimmer control on the factory headlight switch.  With a voltmeter you will see the voltage rise and fall with the adjustment.  Turn the parking lights off and test again.  You should have no reading. Use a wire tap connector and insert it on the correct wire.  Here we have run all of the gauge illumination wires (2 white) into a blue male spade terminal and plugged it into the red wire tap connector.