Originally Posted by Tonny LR
Color coding for 12v wiring, is the red wire positive same as car battery?
For one thing, most +12V wiring in a typical car is not red; for instance, the cap over the positive cable on the battery is typically red, but the cable attached to it is often (including on every vehicle I own) black. You can't count on colour coding unless it is shown a wiring diagram specific to that wire in that vehicle... and some joker hasn't changed it.
Red in the wiring from a tug to a trailer using the original Bargman scheme for their 7-way connector is left combined turn/stop. In the SAE standard J560 which applies to the entirely different 7-way connector used on commercial trucks (and in European 12N and 13-pin trailer connections), red is the stop (brake light) wire. In the wires attached to common trailer brake controller, red is the signal from the brake pedal switch.
In most trailers that I've seen, both battery connections and power to stuff such as lights is black for positive and white for negative (ground).
So... specifically where are you asking about? Escape interior lights? The furnace wiring (like Myron's post