That pink/yellow lead to the ignition is only at +12 volts when the starter is energized. During the run mode, there is only 9 volts or less on that pair of wires due to the resistance wire in the pink lead.

You can get switched +12 volts from the fuse block under the dash from a terminal near the center of the block labeled "IGN". I would guess the A/C system needs more amperage than the pink/yellow leads could provide, anyhow. Also it needs 12 volts.