[rotorwrench]

Accessory is switched with both the Acc position and the Ign position for running. A lot depends on how long the terminals are and whether it can be on when only the accessory position is selected.

Make sure the additional circuit is fuse protected where ever you connect it. Connecting to Bat will not be in the switched category and ST is only for intermittent starting function. These older cars still have a lot of functions that are non-switched but things like the heater, the radio, and overdrive are usually switched. That diagram looks to be one of Bauer's diagrams. They do have good diagrams for their products.