Do not establish voltage or polarity from wire colour alone. In a van or RV, factory vehicle wiring, the conversion builder's circuits and later repairs may follow different conventions. The exact circuit diagram and appropriate testing take priority over a generic chart.
Separate the electrical systems first
Identify whether the conductor belongs to the vehicle, the 12V house system, solar PV, communications or 120V AC. The same visible colour can mean different things in these different systems.
| System | What the colour can tell you | What it cannot establish |
|---|---|---|
| Vehicle/house DC | A builder's convention, if documented | Confirmed polarity, fuse rating or conductor capacity |
| Solar PV | Identification within a documented array | Safe disconnection, polarity or string voltage without checks |
| US AC | Standard identification of neutral and equipment-grounding conductors | That the installation is correct or de-energized |
| Control/data | A device- or harness-specific function | Compatibility with a power circuit |
Marine guidance such as ABYC is not a universal RV wire-colour key. Do not copy an unrelated vehicle's harness or a marine drawing into your own conversion.
Common 12V conventions are a starting point
Red positive and black negative are familiar DC conventions, but they are not proof of what a particular RV builder installed. A coloured stripe, printed circuit number or harness identifier may matter more than the insulation colour.
For an existing RV, find the correct builder, model and model-year drawing. Winnebago's wiring-diagram library is an example of the model-specific documentation to look for. It is not a diagram for every RV.
For a new conversion, choose suitable cable and permanent labels within the applicable installation requirements. Document the function, source protection, destination and conductor specification. Do not invent a universal colour for a fridge, pump or fan.
Common US 120V conductor identification
White or gray normally identifies a grounded/neutral conductor; green, green/yellow or bare conductor identifies equipment grounding. Black is commonly used for hot. This is identification context, not an instruction to connect a new circuit by colour.
The OSHA electrical training material explains the distinction between grounded and equipment-grounding conductors. A qualified RV electrician should identify and verify unfamiliar AC wiring; a photograph is not a commissioning test.
Identify before replacing or buying
Record the circuit identifier, actual voltage, polarity/function, source, destination and protective device. Use suitable rated test equipment and follow its instructions. Resistance or continuity testing requires the circuit to be safely de-energized and isolated from sources that can backfeed it.
Do not disconnect unknown wiring on the assumption that switching off a single device removes every source. Shore, inverter, batteries and solar can supply different parts of a van.
Choose size and protection separately
Colour does not establish ampacity, voltage drop, insulation rating or terminal compatibility. Use the AWG sizing guide with the actual load and circuit length, then record the selected conductor and protection in the electrical parts list.
A kit with familiar colours is not necessarily suitable cable. Avoid substituting a rack-battery connector or appliance-specific harness for a general van circuit without documented compatibility.
Leave a clear record for the next repair
Label both ends and accessible junctions, keep the circuit schedule with the van and update it after changes. Confirm the circuit from the record and testing each time; labels are useful evidence, not a substitute for verification. Use the US electrical planner to organize the design and the exact equipment documents to check it.
Frequently Asked Questions
Keep the build moving
Make the next build decision easier.
Get practical diagrams, calculator updates and honest product comparisons in your inbox.
Jack Kennedy is a self-builder who has built two vans. He created Roam Wired to simplify conversion planning and share free tools, supported by affiliate links.
About Jack