TR2/3/3A Control Head Ground?

[luke44]

The wiring diagram shows 5 wires off the control head, and of course there are only 4, the 5th one being ground (black). Does the control head ground itself to the steering column when tightened up with the grub screws? Or is there some separate ground wire I need to make? If so, where does it start and where does it ground to?

I checked lots of threads on the control head, but none address the ground question. Thanks in advance,

 

[TR3driver]

There is no separate ground wire. The contact inside the head is bolted directly to a brass ring that connects to the housing. I'm not sure if the current actually flows through the column, or through the stator tube, but it gets there somehow.