Instrument cluster regulator

Apply 12 volts to the correct pin.
Ground to the correct location.

Because it is electronic you might be able to check the voltage on the correct pin.

Or you can get some 10 watt resisters 10 ohm, 22 ohms and 73 ohms or there about. And put between the correct pin and ground and watch for needle movement.

I'm being vague on which pin because none of us know what you are working on.