Fuel Rack Solenoid Question

[veggie]

Hi All,

I have a fuel rack solenoid that I wish to mount on the Listeroid as a shutdown device.
This was an "ebay special" and came with no manual or wiring directions.
The [PLUS] and [MINUS] terminals are obvious but it also has an [aux.] connection.

Can anyone tell me what this [aux.] terminal is for and whether I need to connect to it?

cheers,
Veggie