Vacuum gauge lighting.
 

The light is not coming on. However, there is power to the unit.
I looked under the console and there is only 1 wire coming out of the bottom, and there is power to it.
If I touch the housing itself on the outside, the test light lights up. But still no light.
How are these grounded? Am I missing the ground wire?
Thanks in advance, its been a long time since I removed the console. Bored right now so I am fixing all the little stuff.

I believe the ground was supplied thru the 2 screws that hold the front of the console to the floor pan. I always add a ground ire from a console top post, underside, to the shifter boot screw.. Your test light is on because you are completing the circuit the same as a ground wire would. Hope this helps.

"Bill"!

2X on what Bill said, extra ground wire is a good move

That's what I did.
I added one from under on the mounting screw to the shifter screw.