Thread: Aux Power for 12 Pin Trailer Plug

Originally Posted by Grant Iddon

I need to install a flat 12 pin trailer plug in place of the round 7 pin.
The number 12 pin needs an auxilary 12v power (ignition on) to trigger the trailer charging system.

Is there a convenient 12v power supply in the rear area that is powered when the ignition is on that I can tap into?

thanks again for any advise

The cargo area cigaret socket can be taped to give you an IGNITION ON signal

BUT, if the WHITE ( S12 ) plug is still in place, there is a FRIDGE circuit that is only on while the motor is RUNNING.

For an OEM solution, you can change the entire towing wiring harness over to 13pin round using LR011211 (I know, that isn't 12 flat, but you can either change the trailer plug or use an adapter). That gives you all the output options you could ask for I think? Pin 10 is 'ignition on'.

There are a few plug connectors hidden behind the rear bumper the harness taps into - no need to pass cables into the body. (Which means the power source you're looking for is already there somewhere, if you want a cheaper but more DIY solution)

That replaces both the 12N/12S sockets, and opens the option of adding an Anderson point in the newly vacant location.

Reading the electrical diagrams, you can pull the left rear tail light off, and loosen the bumper mounting to reveal the trailer wiring plugs. If you're only looking for an ignition feed, grab the red/white stripe.

Originally Posted by drivesafe

The cargo area cigaret socket can be taped to give you an IGNITION ON signal

BUT, if the WHITE ( S12 ) plug is still in place, there is a FRIDGE circuit that is only on while the motor is RUNNING.

The fridge output on my D3 is switched with the ignition. It's active when the ignition is on regardless of whether or not the engine is running. The cargo cigarette lighter socket (like all those in the car) are switched when the ignition is in the Aux position.