I have a 2016 DF70a with a tiller handle. I am trying to add Minn Kota MK 2DC, which is an onboard alternator battery charger. I need to connect a wire to the ignition circuit that is only energized when the key on the tiller arm is turned on. Searching the internet has led me to believe this wire is either purple or gray. Any ideas where I could make this connection?