switched 12v power

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I have a 2009 sn 196 with the keyless ignition and looking for a "switched" 12v power source under the dash. I'll be running the power through a relay switch that will be able to turn off the heater when the engine is not running

Does anyone know what color wire, or where I can find a "switched" 12v source under the dash??

I do not what to poke around with a volt meter because of the bus electonics there

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12v switched power

the purple ignition wire at connector P2 of the gateway under the instrument pod of a Team/Limited or at the ignition switch of a signature