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Question:
Does the black 12v wire stay hot, even when the truck isnt running with no lights on?
asked by: Brian
Expert Reply:
The 12V wire at the vehicle-end trailer connector being hot even when the truck is off can vary depending on the application. For all aftermarket hardwiring installations of a 7-Way wiring harness, the 12V wire will be hot at all times, even when the truck is off and no lights are on in the trailer. This is because the 12V power wire is ran from the vehicle battery, then typically to a circuit breaker, then to the trailer connector.
In OEM applications, it will vary depending on the make of the truck. For Chevrolet and Dodge trucks, the 12V wire will always be hot, even when the truck is off.
Ford trucks can vary depending on the year and make. Some Ford trucks have a relay that requires the ignition to be on for the 12V wire to have power. Other Fords will have a hot 12V wire all of the time. I believe Toyota trucks are also this way.
