Which is the negative wire

LammyWinn

So I’ve been trying to tap the side marker light on the nuCamp Tab 400. Both wires are yellow. 

Context: I’m trying to tap the side marker light to power my rear backup camera. 

LammyWinn

NM. Pulled out the wire more and it’s green and white. I’ll test those. 

manyman297

I'm not an electrician but I believe 12v systems allow you to interchange either wire. So it doesn't matter which wire you use. I've done a bunch of 12v landscape wiring and positive/negative didn't apply to that.

You might have a different situation than mine but have you considered tapping into the rear license plate light? Assuming you're putting the camera on the backend of the trailer, you can easily run the wire through the existing hole for the license plate light (you just have to pull down the rear bumper cover. Somebody posted photos of this...maybe trying searching "400 backup camera"...it was earlier this year I think.

ScottG

I'll bet a nickel the white is the negative.  :-)

BrianZ

Yep, green is pos in our 320, and it will likely matter to the camera, if not the light.  And if you want to be certain, a voltmeter/multimeter should indicate polarity - where the red test lead is positive, if the displayed reading has a minus sign in front of it, then red is on the negative wire.

fstop32

I'll throw my nickel in with you @ScottG!  One of my "waiting on parts" mods was cleaning up wiring in the rear and mine was positive green and negative white for the side marker lights.

CharlieRN

A cheap VOM (often less than $5 at places like HF) can help sort things out for you and will come in handy for other electrical chores as well. 

ScottG

Some recent projects have rekindled my relationship with the T@B wiring. Although there is a rainbow of colors in there (not always used consistently) so far all the original 12V DC negative wires I've located have been white.

Regardless, I still advocate verifying everything--with a meter and/or visually--before making any new connections.

On a related note, I also advocate for shelling out for two spools of different colored wire when adding circuits for your own projects. Being cheap and using the same colored wire for both legs of a circuit just creates unnecessary confusion. Don't ask me how I know...  ;-) 

AnOldUR

If you don’t have a meter, any 12v device with leads (a light is best) can be used to test polarity. Connect it between one of the wires in question and a ground (frame). If the device works, it’s the positive wire. If it doesn’t, try the other wire.