What Color Wire Is for Brake Lights?
There isn’t a single universal brake-light wire color on vehicles. On most U.S. trailers, the brake-light function shares the turn-signal circuits: yellow is typically left stop/turn and green is right stop/turn. Many aftermarket 3‑wire lamps use red for the brake (bright) lead. On passenger vehicles, colors vary by make and model, so you should verify with a wiring diagram or a test light/multimeter.
Contents
Why There’s No One-Color-Fits-All Answer
Automakers use different color codes across models and years, and many modern vehicles route brake-light commands through a body control module (BCM) rather than a simple two-wire switch. International markets also differ: some vehicles combine stop and turn signals in one filament (red), while others separate them (amber turn, red brake). Because of these variations, relying on color alone can lead to mistakes—verification is essential.
Standard Trailer Wiring Colors in the U.S.
Trailer connectors follow widely adopted color conventions, and on 4- and 7-way systems the brake-light function is combined with turn signals. This makes trailer color codes a reliable reference when wiring or troubleshooting tow connections.
4-Way Flat (and 5-Way Flat) Connectors
The 4-way flat is common for small trailers. It carries ground, tail/running, and the two combined stop/turn circuits. Many 5-way flats add a reverse/lockout function but keep the same brake/turn colors.
- White: Ground
- Brown: Tail/Running lights
- Yellow: Left Turn/Stop (left brake light)
- Green: Right Turn/Stop (right brake light)
- (5-way) Blue: Often reverse lockout or reverse lights on boat/marine trailers
Because the stop and turn are combined, the left brake light energizes via yellow and the right via green. If one side’s brake light is out, inspect the corresponding yellow or green circuit first.
7-Way RV Blade (SAE J2863 pattern)
The 7-way RV blade connector is standard on many trucks and larger trailers. It separates auxiliary and brake-control functions but keeps the left/right stop/turn color conventions.
- White: Ground
- Black: 12V Battery/Aux power
- Yellow: Left Turn/Stop (left brake light)
- Green: Right Turn/Stop (right brake light)
- Brown: Tail/Running lights
- Blue: Electric trailer brakes (controller output—different from brake lights)
- Purple: Reverse/Backup (center pin)
Note the distinction between blue (electric trailer brake controller output) and the yellow/green stop/turn circuits. The blue wire controls trailer brake actuators and is not a brake-light feed.
Passenger Vehicles: Colors Vary—Don’t Guess
On cars, SUVs, and pickups, wire colors for brake lights are not standardized. The high-mounted center brake light (CHMSL) often has its own dedicated feed, while the left/right lamps may be combined with turn signals. Depending on the automaker and model year, the brake-light output from the pedal switch can be any number of colors. That’s why identification by testing is the safe approach.
Aftermarket/Universal 3-Wire Tail/Brake Lamps
Many universal LED tail/brake assemblies come with simple pigtails that use common, though not legally mandated, color conventions. Always confirm with the product’s diagram or a test.
- Red: Brake light (bright)
- Black: Ground (sometimes white instead)
- White or Brown: Tail/Running (dim)
- Yellow (if present on turn/brake combos): Turn/Brake input for one side
Manufacturers can deviate from these norms. If colors don’t match documentation, test the leads with a 12V source to see which function activates.
How to Positively Identify Your Brake-Light Wire
Because colors can mislead, the definitive method is to test the circuit at the brake-pedal switch, CHMSL, or lamp connector with a multimeter or test light.
- Locate the brake-pedal switch: It’s mounted near the top of the brake pedal arm. Modern vehicles may use a multi-wire sensor.
- Identify the power and output leads: One wire is fused power (often hot with ignition on). The brake-light output wire goes to 12V only when the pedal is pressed.
- Test with a meter or test light: Probe each wire. Press the pedal; the correct brake-light wire will switch from 0V to ~12V.
- Verify at the CHMSL or rear lamp: The center brake light usually has a dedicated feed that’s hot only on brake. This can be easier to tap for add-ons like a trailer module or a dashcam trigger.
- Watch for BCM/CAN-bus systems: Some cars don’t provide a simple high-current brake wire; instead, a low-current signal goes to a BCM that powers the lights. In these cases, use a vehicle-specific harness or a logic-compatible interface.
- Document and protect: Once identified, label the wire, use solder/heat-shrink or sealed crimp connectors, and add an inline fuse if you’re powering accessories.
This procedure removes guesswork and protects sensitive electronics, ensuring your connection is both correct and reliable.
Safety and Best Practices
Working around modern vehicle wiring calls for care to avoid damaging modules or compromising safety systems.
- Avoid yellow SRS/airbag harnesses entirely; never tap into them.
- Disconnect the negative battery terminal before splicing; observe proper memory/settings procedures for your vehicle.
- Use a wiring diagram from the service manual or a reputable database for your exact year/make/model.
- Use sealed connectors and quality grounds to prevent corrosion and voltage drop.
- For trailer lighting on modern vehicles, prefer a powered, vehicle-specific trailer module instead of hard splices.
Following these guidelines reduces the risk of faults, false warnings, or BCM damage and helps ensure long-term reliability.
Summary
There isn’t a universal brake-light wire color on passenger vehicles. In U.S. trailer wiring, yellow (left) and green (right) typically carry the combined stop/turn circuits, while many aftermarket 3-wire lamps use red for the brake lead. Because automaker color codes vary widely, the only dependable method is to verify the brake-light wire with a wiring diagram or by testing the circuit at the brake switch, CHMSL, or lamp connector.
What is the 3 color code wire?
In a standard US electrical system, for 120/208/240V circuits, a 3-wire color code identifies the phases, neutral, and ground: Black for Phase 1, Red for Phase 2, Blue for Phase 3, White for Neutral, and Green or green with yellow stripes for the protective Ground wire. It is essential to be aware of this standard and also to know that variations exist in other parts of the world or for higher voltages, and local codes should always be followed.
Standard US 3-Wire Color Code
- Black wire: Phase 1 (L1)
- Red wire: Phase 2 (L2)
- Blue wire: Phase 3 (L3)
- White wire: Neutral (N)
- Green or Green with Yellow Stripe: Ground (or Earth)
Important Considerations
- Single-Phase vs. Three-Phase: This code is for three-phase systems. For single-phase 120V circuits, you would typically see Black for hot, White for neutral, and Green for ground.
- Higher Voltages: For higher voltage industrial applications (e.g., 277V/480V), the colors can change. Brown is used for L1, Orange for L2, and Yellow for L3, while gray is used for neutral and ground.
- International Variations: Wiring color codes differ significantly in other countries. For example, in the UK and other parts of Europe, Brown is used for live, Blue for neutral, and Green/Yellow for earth.
- Safety: Always follow local electrical codes and regulations, as they may differ from these general standards. Consulting a qualified electrician is recommended to ensure correct and safe wiring.
What is the color of a brake light?
red
As such, brake lights are universally colored in red in order to abide by these color recognition norms—since red often signals a stop, it only makes sense to keep brake lights and rear running lights colored in red.
What are the three wires for the brake light?
The first wire is the ground wire, which is typically black. The second wire is the power wire, which is typically red. The third wire is the brake light wire, which is typically white.
How are brake lights wired?
Brake light wiring involves a circuit powered by the vehicle’s battery, traveling through a fuse and a brake light switch located near the brake pedal, and then to the brake light bulbs. Pressing the pedal activates the switch, completing the circuit and illuminating the lights. While the basic principle is consistent, the exact wiring can vary by vehicle, so consulting a wiring diagram specific to your make and model is recommended for detailed diagnosis or repair.
This video demonstrates how to wire brake lights for a classic car or truck: 53sIn The Shop TVYouTube · May 3, 2025
How it Works
- Power Source: The system draws power from the car’s battery.
- Fuse Protection: Power flows from a fuse box to protect the circuit.
- Brake Light Switch: The power then goes to a brake light switch located under the dash, near the brake pedal.
- Activation: When you press the brake pedal, the switch closes, allowing power to flow.
- Wiring Harness: This power then travels through a wiring harness to the brake light bulbs.
- Ground: A ground connection is essential for the circuit to complete, typically a connection to the vehicle’s chassis.
Common Components & Considerations
- Brake Light Switch: This is the key component that turns the lights on and off.
- Wiring Harness: A series of wires connecting the components of the system.
- Bulb Sockets: Where the brake light bulbs are installed and connect to the harness.
- Ground Connections: Crucial for completing the circuit, often connected to the vehicle’s frame.
Troubleshooting Basics
- Check the Bulbs: Ensure the bulbs are not burnt out.
- Test the Switch: Use a test light to check for power at the brake light switch before and after pressing the pedal.
- Examine the Ground: Make sure the ground connection is secure and free of corrosion.
- Use a Wiring Diagram: For a definitive diagnosis, locate and use a wiring diagram specific to your vehicle’s make and model.
You can watch this video to learn how to troubleshoot brake light problems: 58sWilson Auto RepairYouTube · Oct 24, 2023
