Gauge Installation on a 6.6L Duramax

The top arrow in the picture above shows a wire tap connector attached to the vehicles instrumentation dimmer wire.  Once again test this source with your test light or voltmeter.  Turn your parking lights on.  With a test light you should see it 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.

The bottom arrow shows a possible source four a ground.  If you decide to terminate your ground wires here you will need an additional 6mm nut.  Attach all wires that need to be grounded (Pyrometer Black, Trans Gauge Black, and Illumination Black) in a suitable ring terminal.  Place the ring terminal over the threaded stud shown here, and follow with an additional 6mm nut.