Read with DVM. 12v is from the fuse panel marked gauges so I can dim the gauge lights along with the regular factory gauges. 12v is read at the 12v terminal at back of gauge. 12v power source for gauge is from the fuse panel, switched 12v.
How bout clarifying this one a lil bit?
5 connections on an autometer electric gauge:
3 studs, 2 wire pigtails.
Stud1: Gauge power
Stud 2: Sender
Stud 3 Ground
Black wire: illumination lamp ground
White wire: Illumination lamp power
The grounds can be connected together, and then run to a solid ground screw on the cars dash structure.
Gauge power needs to go to the IGN FUSED circuit, it is the 3rd spade terminal from the top in the pic below.
The white wire needs to go to LAMPS, the second connection down. This one dims when you turn the headlight switch.
4 male spades in a 67 fuseblock, top to bottom:
ACC FUSED: on in RUN and ACC
LAMPS: on when headlight switch is on, variable output controlled by twisting the headlight switch knob.
IGN FUSED: on in RUN only
BAT FUSED: on all the time