In the typical RV, you are likely to find several different color codes in existance. From the chart above, you are likely to encounter several different color codes in the same trailer!

• RED/BLACK: The most typical color code, by convention at least, is 12V represented by RED, and GND represented by BLACK.

• RED/WHITE: An alternate color code, but not as common is 12V represented by RED, and GND represented by WHITE.

• COLOR/WHITE-COLOR STRIPE: This scheme is copied from the telephone industry. Basically, each SOLID color represents 12V, and the WHITE wire with the same color stripe represents GND. Often you will find this kind of wiring from a distribution panel, where each solid color represents a different circuit. Thus, it allows easy indentification of what circuit each wire is on.

• RED/YELLOW: Also called "Safety Wire". You won't likely find this color code in a RV, but the boating industry is going to RED to represent 12V, and YELLOW to represent GND. In larger boats having 120VAC wiring co-located with 12VDC wiring, using YELLOW for 12V Ground prevents mistaking 120VAC BLACK (HOT) for 12VDC BLACK GND, and the inadvertant connection of 120VAC to GND. Since RVs also have 120VAC and 12VDC circuits, this would be a good idea (although the COLOR/WHITE-STRIPE scheme would accomplish the same goal).

• Finally, many Chinese components (a lot of which are used in RVs) use BLACK for 12V and WHITE for GND. This is a poor practice as this is the exact same color code used in 120VAC wiring. So be very aware of any wiring you do in your RV when you encounter Chinese products.

The National Electrical Code (NEC) specifies BLACK as ungrounded 120VAC (called HOT - because it is above ground), WHITE (called NEUTRAL) is typically grounded 120VAC, and GREEN or bare wire for GROUND. As well, RED is often used to designate SWITCHED 120VAC HOT (ungrounded) wiring. For example, a 3-Way switch would typically have RED wires between the two switch poles.

And to confuse matters further, the NEC allows using a different color wire, by wrapping tape of the proper color at each end of the wire. You are likekly to find this practice in a switch where Romex type wire is used to wire the switch, and the WHITE wire has RED tape at each end to designate this is a switched/hot wire rather than the common.

Some trailers also have 240VAC wiring. Trailers wired for 50A service are 240VAC. The wiring scheme is BLACK = L1, RED = L2, WHITE = Common, GREEN = GND. L1 and L2 are Leg 1 and Leg2, and are both "HOT" (above ground); the wiring that provides 240VAC. Neutral is typically attached to Ground at the power pedestal. Typically 240VAC terminates at the breaker panel where is is split into 120V circuits. However, some high-end RVs having washer and dryers as well as air conditioners may use 240VAC for these appliances.

And if that is not confusing enough, when we look at trailer wiring codes, there is more inconsistancy. For some unknown reason, the RV industry decided to use their own color code for the 7-Pin trailer wiring color code. Your tow vehicle though will likely have an SAE (Society of Automotive Engineers) standard color code. And in fact, when you buy a 7-Pin receptacle, it might have either SAE or RV color code etched into it.

Fortunately though, even though the color code is different, the functions are thae same. For example, Pin 1-7 for the RV connector has the same function as the SAE connector Pin 1-7.

I have seen some whacky wiring jobs in my days looking at RV taillights. In some examples, a 4 Wire SAE cable is interconnected to a 7 Wire RV cable, resulting in the color code of the wires changing along the length of the wiring harness (especially the Left and Right turn signal wires). Other examples are the color codes not matching at the taillight connection itself.

When tracing wiring, it is often useful to use a voltmeter to confirm your findings.