Adding passing lights (also known as auxiliary or driving lights) to your motorcycle not only enhances visibility but also increases your presence on the road. Whether you’re installing them for style, safety, or better nighttime performance, proper wiring is essential for reliability and longevity.
This guide explains how to wire passing lights on a motorcycle safely — covering tools, wiring diagrams, relays, switches, and expert tips for Harley-Davidson and other major brands.
💡 Quick Answer: Use a Relay and Inline Fuse for Safety
The best way to wire passing lights on a motorcycle is by using a **12V relay** and an **inline fuse** to protect your electrical system. The lights connect to your battery or accessory power, controlled by a switch on your handlebars or ignition circuit.
In short: Power → Fuse → Relay → Switch → Passing Lights → Ground.
🧰 Tools and Materials You’ll Need
- 12V passing lights or LED auxiliary lamps
- 12V 30-amp automotive relay
- Inline fuse holder and 10A–15A fuse
- Switch (handlebar or dashboard mounted)
- 18-gauge electrical wire (red, black, and yellow)
- Wire connectors or soldering kit
- Heat shrink tubing and electrical tape
- Crimping tool and wire stripper
- Multimeter for voltage testing
- Zip ties or wire loom for cable management
- Eagle Lights LED passing light kit (for plug-and-play simplicity)
Pro Tip: Always disconnect your motorcycle’s negative battery terminal before starting any wiring project to prevent shorts or sparks.
⚙️ Step 1: Choose Your Power Source
Decide where your passing lights will draw power from. You have two main options:
- Direct Battery Connection: Provides constant power even when the bike is off. Best for independent control via a switch.
- Switched Power Source (Ignition): Only powers the lights when the ignition is on — safer and prevents draining your battery if you forget to turn them off.
Recommendation: Use a switched ignition source if possible. This ensures the lights automatically turn off when you stop the engine.
🔋 Step 2: Install an Inline Fuse
An inline fuse protects your motorcycle from electrical overloads or short circuits.
- Cut a short piece of wire from the battery’s positive terminal.
- Install the inline fuse holder close to the battery — within 6 inches is ideal.
- Insert a 10A–15A fuse, depending on your light’s wattage.
This fuse ensures any surge or short will blow the fuse instead of damaging your wiring or electrical components.
🧠 Step 3: Wire the Relay
A relay ensures your lights get full power directly from the battery while only drawing minimal current from the switch. Here’s how a 4-pin relay typically connects:
| Relay Terminal | Connection | Description |
|---|---|---|
| 30 | Battery positive (+) through inline fuse | Main power input |
| 87 | To passing lights (+) | Power output to lights |
| 85 | To ground (-) | Completes circuit for relay coil |
| 86 | To switch output | Activates relay when switch is on |
Pro Tip: Mount the relay near your battery or under your seat in a dry location. Use zip ties or mounts to secure it away from heat and moving parts.
🪛 Step 4: Mount and Wire the Passing Lights
- Install your passing lights on the forks, crash bar, or front frame using supplied brackets.
- Connect the positive wire from both lights to the relay’s terminal 87.
- Connect each light’s negative wire to a clean, paint-free frame ground or directly to the battery negative terminal.
- Route the wiring neatly along the frame and secure it with zip ties.
Keep wires clear of your front suspension, steering, and engine heat sources.
⚡ Step 5: Connect the Switch
Install a switch to control when your passing lights turn on:
- Handlebar-mounted rocker or push-button switches are the most convenient.
- Connect one side of the switch to an ignition-switched 12V power source (like the headlight circuit).
- Connect the other side to relay terminal 86.
When you flip the switch, it triggers the relay to send power to the lights. Use weatherproof switches to prevent corrosion and shorts.
💡 Step 6: Test the System
- Reconnect your motorcycle’s battery.
- Turn on the ignition (if using switched power).
- Flip your light switch — your passing lights should illuminate immediately.
- Test both high and low beams to ensure compatibility and brightness.
If the lights flicker, double-check your grounds and relay wiring. Consistent brightness means your setup is correct.
🌧️ Step 7: Weatherproof and Secure Your Wiring
Riding in rain or snow requires waterproofing your electrical connections to prevent corrosion or short circuits:
- Use heat shrink tubing over soldered or crimped joints.
- Wrap all exposed wires with electrical tape.
- Apply dielectric grease to connectors and switch terminals.
- Bundle wires neatly with zip ties and avoid tension at connection points.
Waterproofing your system ensures long-term reliability, especially for touring or all-weather riders.
🔧 Step 8: Adjust Beam Alignment
Proper alignment ensures maximum road visibility without blinding oncoming drivers:
- Position your passing lights about 1–2 inches below your headlight beam center.
- Aim them slightly downward and outward for balanced coverage.
- Test at night — the beam should extend 100–150 feet ahead without excessive glare.
Pro Tip: Pair your new passing lights with an Eagle Lights LED headlight for the brightest, most uniform visibility setup available.
⚙️ Step 9: Optional — Integrate with High Beam
Some riders prefer their passing lights to turn on automatically with the high beam:
- Tap the relay trigger wire (terminal 86) into the motorcycle’s high-beam wire instead of a manual switch.
- This way, passing lights activate whenever the high beam is turned on.
Note: Check your local laws — some regions restrict using auxiliary lights in combination with high beams.
🧩 Step 10: Perform a Final Inspection
- Ensure all bolts and brackets are tight.
- Double-check fuses, relays, and grounds.
- Inspect that wiring doesn’t rub against sharp edges or moving parts.
- Start the bike and test again under full electrical load (brake lights, turn signals, and horn).
Your passing lights should remain stable and bright, even with other accessories running.
💬 Frequently Asked Questions (People Also Ask)
What are passing lights on a motorcycle?
Passing lights (or auxiliary lights) are additional front lights designed to improve road illumination and make your motorcycle more visible to others.
Do passing lights drain the battery?
LED passing lights draw minimal power. Using a relay and fuse ensures safe operation without draining your battery.
Can I wire passing lights without a relay?
Technically yes, but it’s not recommended. A relay prevents switch overload and ensures your lights get full voltage.
Are motorcycle passing lights legal?
Yes — as long as they’re white or amber and aimed correctly. Avoid using flashing or colored lights on public roads.
How many amps do passing lights use?
Most LED passing lights use 2–5 amps total. Always size your fuse and wiring accordingly.
Can I connect passing lights to my headlight switch?
Yes. Many riders wire their relay trigger into the low- or high-beam circuit for automatic operation.
🏁 Final Thoughts: Wire It Right, See the Night
Installing passing lights is one of the best upgrades you can make for nighttime visibility and safety. With a relay, fuse, and weatherproof wiring, you’ll have reliable lighting that lasts for years — and adds a stylish look to your motorcycle.
For riders who prefer plug-and-play simplicity, Eagle Lights LED passing light kits come pre-wired for easy installation — delivering powerful, uniform light that makes you visible from every angle.
Ride safe. Ride bright. Wire smart.
