Campervan Wiring Colour Codes: UK Standard Guide
Colour consistency in your campervan wiring is not a cosmetic choice — it is a safety practice that prevents you, or anyone who works on your van after you, from connecting live wires to the wrong terminals, shorting battery cables, or receiving a 230V shock. A single crossed wire can destroy electronics, blow fuses, or cause a fire. This guide covers every colour standard you need to know for a UK campervan build.
For the full picture of safe wiring practices, see our campervan wiring safety guide. If you are still routing cables, our guide on campervan cable routing covers the physical side of getting wires from A to B safely.
Design Your Wiring Layout First
Our free calculator generates a complete wiring diagram for your campervan, with correct cable sizes and colour-coded circuits. Know exactly what goes where before you start.
12V DC Wiring Colour Standards
The 12V DC system is the backbone of your campervan electrical installation — it powers your lights, fridge, USB sockets, water pump, and most other daily-use devices. The colour convention is simple and universally understood.
The Core Rule: Red and Black
| Conductor | Colour | Function |
|---|---|---|
| Positive (+) | Red | Carries current from the battery to the load |
| Negative (−) | Black | Returns current from the load to the battery |
This is the standard used across virtually all 12V automotive, marine, and campervan installations in the UK. Red is positive. Black is negative. Never deviate from this on your main DC distribution wiring.
Reversing Polarity Destroys Equipment
Connecting a 12V device with reversed polarity (positive to negative and vice versa) can instantly destroy electronics, blow internal components, or in the worst case cause a fire. Consistent colour coding is your primary defence against polarity reversal. If you ever find yourself unsure which wire is positive, stop and test with a multimeter before connecting anything.
Extended 12V Colour Coding for Multiple Circuits
When you have multiple 12V circuits — lighting, fridge, water pump, USB sockets, fan — using red and black for every circuit makes it difficult to identify which pair of wires belongs to which circuit. The solution is to use different colours for the positive feed of each circuit while keeping all negatives black.
A common approach used in professional campervan builds:
| Circuit | Positive Wire Colour | Negative Wire Colour |
|---|---|---|
| Main battery feed | Red | Black |
| Lighting | Yellow | Black |
| Water pump | Blue | Black |
| Fridge | Orange | Black |
| USB / phone charging | Green | Black |
| Fan / ventilation | White | Black |
| Auxiliary / spare | Brown | Black |
There is no single mandatory standard for circuit colours in a 12V DC system — unlike 230V AC wiring, which is regulated. The table above is a widely used convention, but the most important thing is consistency within your own build. Pick your colours, write them down, and stick with them.
Document Your Colour Scheme
Create a simple colour chart on paper or in a notes app and keep it with your van documentation. Even if you remember every wire today, you will not remember six months from now when something needs troubleshooting. Stick a laminated copy of your colour chart inside the electrical cupboard or behind a panel near the fuse box.
Tinned vs Untinned Copper
The colour of the insulation matters, but also consider what is inside it. For campervans, use tinned copper cable (often called marine-grade or tri-rated cable) wherever possible. Tinned copper resists corrosion far better than bare copper in the damp environment of a van. Tri-rated cable is available in a wide range of insulation colours, making circuit identification easy.
230V AC Wiring Colour Standards
If your campervan has a mains hook-up (shore power) system, the 230V wiring must follow the UK standard colour codes. Unlike 12V, these colours are regulated by BS 7671 and are not optional.
Current UK Standard (Post-2006)
| Conductor | Colour | Function |
|---|---|---|
| Live (L) | Brown | Carries the supply current |
| Neutral (N) | Blue | Return path for current |
| Earth (E/CPC) | Green/Yellow (striped) | Safety conductor — carries fault current to trip protective devices |
These colours apply to all flexible cables (like the hook-up lead) and to the fixed wiring inside the van (twin-and-earth cable, where the live core is brown-sleeved, the neutral is blue-sleeved, and the earth is bare copper sleeved with green/yellow).
Pre-2006 Colours (Old Standard)
You may encounter the old UK colour standard in second-hand components, older vans, or inherited equipment:
| Conductor | Old Colour | New Colour |
|---|---|---|
| Live | Red | Brown |
| Neutral | Black | Blue |
| Earth | Green/Yellow | Green/Yellow (unchanged) |
Old Colours Create Dangerous Confusion
The old 230V live colour (red) is the same as the 12V positive colour. The old 230V neutral colour (black) is the same as the 12V negative colour. If you have any pre-2006 mains cable in your van, re-sleeve or replace it immediately to avoid a potentially fatal mix-up between your 12V and 230V systems.
Three-Phase (Rare in Campervans)
Most campervans will never encounter three-phase power, but for completeness: the three phases are Brown (L1), Black (L2), and Grey (L3), with Blue as neutral and Green/Yellow as earth.
Vehicle Wiring Colours (Existing Loom)
Your base vehicle — Transit, Sprinter, Ducato, or whatever it is — has its own factory wiring. If you tap into the vehicle loom for accessories like a radio, interior lights, or ignition-switched feeds, you need to understand the vehicle's colour scheme.
Common Vehicle Wiring Colours
Vehicle manufacturers do not all use the same colour scheme, but some conventions are common across European vehicles:
| Function | Common Colour | Notes |
|---|---|---|
| Permanent 12V (battery) | Red or Red/White | Always live, direct from battery |
| Ignition-switched 12V | Yellow or Green | Live only when ignition is on |
| Accessory 12V | Orange or Violet | Live in accessory position |
| Ground / Earth | Brown or Black | Connected to vehicle chassis |
| Illumination | Grey or White | For dimming dash lights |
These vary between manufacturers. Always check the wiring diagram for your specific vehicle. Ford, Mercedes, Fiat/Stellantis, and VW all have their own colour conventions. Workshop manuals (Haynes or manufacturer-specific) are the definitive reference.
Never Assume — Always Verify
Even if a forum post says your van's ignition feed is a yellow wire behind the steering column, verify it with a multimeter before tapping into it. Vehicle variants, model years, and factory options mean the wire colours in your specific van may differ from what someone else found in theirs.
Labelling Best Practices
Colour coding gets you most of the way, but labelling closes the gap completely. Professional installations always have labelled cables — and your campervan should too.
Label Both Ends of Every Cable
A cable disappears into a wall cavity or under a floor. By the time it emerges at the other end, you cannot tell which cable it is by colour alone (especially if multiple circuits share the same colour). Label every cable at both ends — at the fuse box end and at the device end.
Labelling Methods
| Method | Cost | Durability | Readability |
|---|---|---|---|
| Brother P-Touch label maker | £20-£30 | Excellent (laminated) | Excellent |
| Printed cable wrap labels | £10-£15 per pack | Very good | Good |
| Permanent marker on white heat shrink | £5 | Good | Moderate |
| Masking tape and pen | £2 | Poor (falls off) | Moderate |
A Brother P-Touch label maker is the best investment for a professional finish. The labels are laminated, self-adhesive, and survive the heat, cold, and moisture inside a campervan for years.
What to Write on Labels
Include enough information that someone unfamiliar with your system can understand it:
- Circuit name: "Lighting", "Fridge", "Water Pump"
- Fuse reference: "F3" or "Fuse 3" (matching the fuse box position)
- Cable size: "2.5mm2" or "4mm2" (helpful when replacing)
- Polarity: "+" or "−" if the colour is ambiguous
Example label: FRIDGE +VE | F5 | 4mm2
Keeping 12V and 230V Separated
One of the most important safety rules in a campervan is maintaining physical separation between your 12V DC and 230V AC wiring. This prevents accidental contact and makes it immediately obvious which system is which.
Separation Rules
- Run 12V and 230V cables in separate looms or conduits
- Never bundle 12V and 230V cables together in the same trunking
- Cross cables at 90 degrees where they must cross, to minimise parallel proximity
- Use different-coloured conduit or trunking for each system (grey for 230V and black for 12V is common)
- Keep a minimum of 50mm physical separation where cables run in parallel
Visual Identification at a Glance
If you open an electrical panel and see red, black, yellow, blue (with coloured insulation), and green wires — those are your 12V DC circuits. If you see twin-and-earth cable with brown, blue, and green/yellow cores — that is your 230V AC. The colour difference is immediately obvious, which is exactly the point.
Common Colour Code Mistakes
Using Blue for Both 12V Negative and 230V Neutral
Blue is the UK standard for 230V neutral, but some builders also use blue as a 12V circuit colour. This creates confusion when both systems are in the same panel. Avoid using blue in your 12V colour scheme altogether.
Using Brown for 12V Auxiliary
Brown is the UK standard for 230V live. Using it as a 12V circuit colour invites dangerous misidentification. Reserve brown exclusively for 230V live conductors.
No Labels, No Documentation
Building a system with perfect colour coding and then not labelling anything is half a job. The colours help, but labels confirm. Future you (or the next owner) will thank present you for labelling every cable.
Mixing Old and New 230V Colours
If you buy a second-hand mains hook-up lead with old-standard colours (red/black/green-yellow), replace it. Do not use old-colour cable anywhere in your van — the risk of confusion with 12V wiring is too high.
Quick Reference Summary
| System | Positive / Live | Negative / Neutral | Earth / Ground |
|---|---|---|---|
| 12V DC | Red | Black | Chassis or dedicated earth bus |
| 230V AC (UK) | Brown | Blue | Green/Yellow |
| Vehicle body | Varies | Brown or Black | Chassis |
Print this table and keep it visible in your build area while you work. When in doubt, refer to it.
For more on correct cable sizing for each of these circuits, see our campervan cable sizes guide. And for a complete walkthrough of safe wiring practices, start with the wiring and safety pillar guide.
FAQ
Can I use any colours I want for 12V wiring?
Technically yes — there is no legal standard for 12V DC wiring colours in a self-build campervan. However, red for positive and black for negative is so universally understood that deviating from it is asking for trouble. Use the standard red/black convention and add different colours for individual circuit positives if needed.
What if I run out of a specific colour cable?
It is better to wait and order the correct colour than to substitute. If you absolutely must use a different colour in a pinch, label the cable at both ends immediately and add a note in your wiring documentation. However, for main battery feeds, always use red (positive) and black (negative) without exception.
Do I need to follow UK colour codes if I am building for personal use only?
Following the standard is strongly recommended even for personal builds. If you ever sell the van, have it inspected, or need emergency repairs, non-standard colours will confuse anyone who works on it — including future you. If an insurance assessor finds non-standard wiring after an incident, it could affect your claim.
Why is the earth wire green and yellow?
The green/yellow striped pattern was adopted internationally to make the earth conductor instantly recognisable, even for people with colour blindness. The two-colour stripe is unique among electrical conductors and cannot be confused with any single-colour wire. It has been the standard in the UK since 1977.