How To Wire LED Light Bar Safely & Easily

Can I wire an LED light bar myself? Yes, you can wire an LED light bar yourself with basic tools and a little guidance, making your vehicle safer and more visible. This comprehensive guide will walk you through the entire process of installing and wiring an LED light bar, ensuring a safe and reliable setup. We’ll cover everything from choosing the right components to the final connection.

Wiring an LED light bar might seem daunting, but with the right information and careful execution, it’s a manageable DIY project. Whether you’re adding auxiliary lighting for off-roading, improving visibility for work, or just want a stylish upgrade, a properly wired LED light bar makes a significant difference. This guide aims to make the automotive LED light bar installation process clear and straightforward.

How To Wire Led Light Bar
Image Source: www.superbrightleds.com

Deciphering Your LED Light Bar Wiring Needs

Before you start, it’s crucial to know what you need. The type of LED light bar you have, your vehicle’s electrical system, and how you intend to use the light will all influence the components and wiring approach.

What You’ll Need: A Checklist

Gathering all your supplies beforehand will save you time and frustration. Here’s a list of essential items:

LED Light Bar: The star of the show! Ensure it’s rated for your vehicle’s voltage (usually 12V or 24V).
LED Light Bar Wiring Harness: Many light bars come with one, but if not, you’ll need to purchase a compatible harness. This is the backbone of your setup.
Inline Fuse Holder and Fuse: Crucial for protecting your electrical system from surges. The fuse rating should match the light bar’s amperage draw.
Automotive Relay: Essential for handling the high current of the light bar, preventing your switch from burning out. A 12V/30A relay is standard.
On/Off Switch: A momentary or latching switch to control your light bar. Ensure it’s rated for the current.
Wire Strippers/Crimpers: For preparing wires and making secure connections.
Wire Connectors: Various types like butt connectors, ring terminals, and spade connectors. Heat shrink tubing is highly recommended for insulation.
Electrical Tape: For securing and insulating connections.
Mounting Hardware: Brackets, bolts, nuts, and washers suitable for your vehicle.
Drill and Drill Bits: If you need to create mounting holes or pass wires through the firewall.
Screwdriver Set: For various mounting and connection points.
Multimeter: To test voltage, continuity, and identify power sources.
Zip Ties: For neat cable management.
Optional: Inline Diode: If you plan to connect the relay to your high beams for automatic activation.

Fathoming the LED Light Bar Wiring Diagram

The LED light bar wiring diagram is your roadmap. Most harnesses come with a diagram, but if yours doesn’t, you can find generic ones online for common setups. A typical diagram will show how to connect LED light bar components like the relay, switch, fuse, and battery.

A basic LED light bar wiring harness typically includes:

Battery Terminal: Connects to the positive (+) terminal of your battery.
Relay Terminal: Connects to the relay’s power input.
Accessory Terminal: Connects to your LED light bar.
Ground Terminal: Connects to a clean ground point on your vehicle.
Switch Terminal: Connects to your dash switch.

Choosing the Right Fuse and Relay

The LED light bar fuse and relay are critical safety components.

Fuse: The fuse protects your wiring and electrical system from overcurrent. A general rule of thumb is to select a fuse that is 25% higher than the light bar’s amperage draw. For example, if your light bar draws 5 amps, use a 6.25-amp fuse, but since fuses come in standard sizes, a 7.5-amp fuse is a good choice.
Relay: A relay acts as an electronic switch. The low-current signal from your dash switch activates the relay, which then handles the high current needed for the LED light bar. This prevents the switch from overheating and failing. A 12V 30A/40A automotive relay is standard and sufficient for most LED light bars.

Installing Your LED Light Bar: Step-by-Step

The physical installation of the light bar is the first step before you even think about wiring.

Mounting the LED Light Bar

The best way to wire LED light bar starts with secure mounting.

Determine Placement: Decide where you want to mount your light bar. Common locations include the roof rack, front bumper, or grille guard. Ensure it doesn’t obstruct your vision or interfere with vehicle operation.
Position Brackets: Hold the light bar in its intended position and mark where the mounting brackets should attach. Use a tape measure and level for precision.
Drill Mounting Holes: If necessary, drill holes for the mounting bolts. For bumpers or body panels, be mindful of what’s behind the drilling area. Use appropriate drill bits for metal or plastic.
Install Brackets: Securely attach the mounting brackets to the vehicle using appropriate hardware. Use washers and lock washers to ensure a tight, vibration-resistant fit.
Mount the LED Light Bar: Place the LED light bar onto the brackets and loosely fasten the bolts. Adjust the bar for proper alignment before tightening everything down. Ensure it’s stable and won’t move with vibration.

Routing the Wiring Harness

Neat and safe wire routing is crucial for longevity and preventing damage.

Identify a Firewall Pass-Through: Most vehicles have a rubber grommet in the firewall that allows you to pass wires from the engine bay into the cabin. If one isn’t available, you might need to drill a new hole, carefully installing a grommet to protect the wires.
Route Through the Firewall: Feed the wiring harness through the firewall. If you have a harness with a separate battery lead and switch lead, route the switch lead into the cabin and the battery lead to the engine bay.
Secure Wiring in the Engine Bay: Use zip ties to neatly secure the wiring harness along the chassis or existing wiring looms. Keep it away from hot engine components, moving parts like belts and fans, and sharp edges.
Secure Wiring in the Cabin: Similarly, route the wiring inside the cabin, keeping it tidy and out of the way. Conceal it under trim panels or carpets where possible.

Connecting Your LED Light Bar: The Wiring Process

This is where the LED light bar power connection and switch wiring come into play. The most common and safest way to connect LED light bar components is using an LED light bar wiring harness with a relay.

Wiring the Relay

The relay is the heart of the circuit, controlled by your switch.

Identify Relay Terminals: Automotive relays typically have five or four terminals. The common ones are:
- 30 (Power In): Connects to the positive (+) terminal of the battery (via the harness).
- 87 (Power Out): Connects to the positive (+) wire of your LED light bar (via the harness).
- 85 (Ground): Connects to a good ground point on your vehicle’s chassis.
- 86 (Trigger): Connects to your dash switch, which in turn connects to a power source (often from the switch’s accessory power).
Connect the Battery Power (Terminal 30): Connect the designated battery lead from your wiring harness to the positive (+) terminal of your vehicle’s battery. It’s best to use a ring terminal for a secure connection.
Connect the Light Bar Power (Terminal 87): Connect the wiring harness lead that goes to your LED light bar to terminal 87 of the relay.
Connect the Ground (Terminal 85): Connect the ground lead from your wiring harness to a clean, unpainted metal surface on your vehicle’s chassis. Scrape away any paint or rust to ensure good conductivity.
Connect the Trigger (Terminal 86): This is where your switch comes in.
- Connect a wire from terminal 86 of the relay to one side of your chosen dash switch.
- The other side of the switch needs to be connected to a fused power source. This can be from the ignition accessory circuit (so the light bar only turns on when the car is on) or directly from the battery (always-on capability). LED light bar switch wiring needs to be planned carefully.

Installing the Fuse Holder

The fuse holder is placed between the battery and the relay.

Locate Fuse Holder: Most wiring harnesses have an inline fuse holder already integrated.
Connect to Battery Positive: The fuse holder should be connected to the positive (+) battery terminal, either directly or via the wiring harness’s battery lead.
Insert Fuse: Ensure you have the correct amperage fuse installed.

Wiring the Switch

The switch controls the relay, allowing you to turn the light bar on and off.

Choose Switch Location: Select a convenient and accessible location for your switch, typically on the dashboard or center console.
Drill for Switch: If needed, drill a hole to accommodate your switch.
Connect Switch:
- Power Input: Connect a wire from a fused accessory power source (or directly from the battery if you want it to be always on) to one terminal of the switch. This is the power that will “trigger” the relay.
- Output to Relay: Connect a wire from the other terminal of the switch to terminal 86 of your relay.

Important LED light bar wiring tips for switch connections:
* If you want the light bar to turn on only when the ignition is on, tap into a fuse that is powered only when the ignition is in the “ON” or “Accessory” position.
* If you want the light bar to be always on, you can connect the switch directly to a fused power source from the battery.

Connecting the LED Light Bar to the Harness

Identify Positive and Negative: Your LED light bar will have a positive (+) and negative (-) wire.
Connect to Harness: Connect the positive wire from the light bar to the output terminal (usually marked) of your wiring harness. Connect the negative wire from the light bar to the ground terminal of your wiring harness. Most harnesses use waterproof connectors for these connections.

Testing Your Setup

Before finalizing everything, it’s crucial to test your work.

Double-Check Connections: Review all your wiring connections to ensure they are secure and correctly made.
Turn on Ignition: Turn your vehicle’s ignition to the “ON” or “Accessory” position.
Test the Switch: Flip your dash switch. The LED light bar should illuminate.
Troubleshoot: If the light bar doesn’t turn on, use your multimeter to check for voltage at the switch, the relay, and the light bar itself. Verify ground connections and fuse integrity.

Advanced Wiring Techniques and Considerations

For more complex setups or specific needs, consider these advanced techniques.

Connecting to High Beams (Optional)

You might want your LED light bar to come on automatically with your high beams.

Using a Diode: To prevent feedback to your vehicle’s computer system, you’ll need to install an inline diode between your high beam wire and the relay’s trigger terminal (terminal 86). The diode allows current to flow from the high beam to the relay but not the other way around.
Wire Tap: Carefully tap into the positive wire of your high beam circuit.

Dual Switches for Multiple Lights

If you have multiple light bars or different types of auxiliary lights, you can use separate switches and relays for each.

Inline Diode for Relay Isolation

In some specialized circuits, a diode might be placed in parallel with the relay’s coil (across terminals 85 and 86) to suppress voltage spikes when the relay deactivates. However, for most standard LED light bar installations, this is not necessary.

Safety First: Essential LED Light Bar Wiring Tips

Safety should always be your top priority.

Disconnect Battery: Always disconnect the negative (-) terminal of your battery before starting any electrical work.
Proper Fuse Sizing: Never use a fuse with a higher rating than recommended.
Secure Connections: Use high-quality connectors and crimp them securely. Heat shrink tubing provides excellent insulation and strain relief.
Protect Wiring: Route wires away from heat, moving parts, and sharp edges. Use grommets when passing wires through metal.
Good Ground: A poor ground connection is a common cause of electrical problems. Ensure your ground point is clean and secure.
Waterproofing: Use waterproof connectors or seal your connections with dielectric grease and heat shrink tubing to prevent corrosion.
Follow Diagrams: Always refer to the specific LED light bar wiring diagram provided with your product or a reliable generic one.

Troubleshooting Common Issues

Even with careful work, you might encounter problems.

Problem	Possible Cause	Solution
Light Bar Won’t Turn On	No power to switch, faulty switch, loose relay connection, blown fuse, bad ground.	Check battery connection, switch wiring, relay pin seating, fuse, and ground connection. Use a multimeter.
Light Bar Flickers	Loose connection, poor ground, insufficient power.	Ensure all connections are tight, especially the ground. Check battery voltage.
Relay Clicks but No Light	Light bar connection issue, faulty light bar, incorrect relay wiring.	Check light bar connections to the harness and the relay’s power output (terminal 87).
Switch Gets Hot	Switch not rated for current, direct wiring without a relay.	Use a relay. Ensure your switch is adequately rated for the amperage.
Light Bar Stays On	Relay stuck in the “on” position, incorrect trigger wiring.	Check trigger wiring (terminal 86). If the relay is faulty, replace it.

Frequently Asked Questions (FAQ)

Q1: Do I need a relay for my LED light bar?

A1: Yes, it is highly recommended. Relays protect your switch from the high current draw of the LED light bar, preventing damage and ensuring a safer system.

Q2: What size fuse should I use for my LED light bar?

A2: The fuse rating should be about 25% higher than the total amperage your LED light bar draws. Check the light bar’s specifications for its power consumption.

Q3: Can I connect my LED light bar directly to the battery?

A3: You can connect the power feed to the relay directly to the battery, but you should never connect the light bar directly to the battery without a fuse and a relay.

Q4: Where is the best place to ground my LED light bar wiring?

A4: Find a clean, unpainted metal surface on your vehicle’s chassis. Scrape away any paint or rust to ensure a solid electrical connection.

Q5: How do I wire the switch for my LED light bar?

A5: The switch acts as a trigger for the relay. Connect one terminal of the switch to a fused power source (e.g., ignition accessory circuit) and the other terminal to the relay’s trigger terminal (usually terminal 86).

Q6: My LED light bar isn’t working after installation. What should I check?

A6: First, disconnect the battery. Then, carefully re-check all connections: battery terminal, ground, relay terminals, fuse, and the connection to the light bar itself. Use a multimeter to test for continuity and voltage.

By following these detailed instructions and safety tips, you can confidently install and wire your LED light bar, enhancing your vehicle’s lighting capabilities safely and effectively. Enjoy your brighter adventures!