Ground Terminal On Ignition Switch?

[George7941]

http://products.pollakaftermarket.c...es/ignition-starter-switches-1064/31-164
This is for heavy trucks and one of the terminals is marked GRD on the switch which I just replaced. If you look at the "larger image" of the back of the switch in the link, it is marked GR. I tested the switch I have and the GRD terminal is not connected to anything - not to the metal body of the switch or to any of the other terminals ( BAT, ACC, IGN, ST), in any position of the switch (Off, Acc, Run, Start).

So what is the terminal for?

 

[CorvairGeek]

Some designs (very common in older GMs) use a ground connection in the 'start' position only, to do a bulb check (temperature idiot light and brake in particular) that might never be seen otherwise.

 

[George7941]

Interesting, good to know. So that would require two extra wires to the switch, one from the circuit (bulbs, in your example) to be grounded and one ground wire if the grounding of the switch body through its mounting cannot be depended on.