Installing auxiliary lights on a motorcycle requires a fused relay circuit, a switched 12V trigger, and careful aiming to improve visibility without blinding traffic.
Most auxiliary-light installs follow the same core sequence: mount the pods where they clear everything, wire them through a fused and relayed circuit, trigger from a switched 12V source, aim the beams, then retorque after vibration settles. Start by disconnecting the battery — that gives you a safe workspace for the whole job.
Mounting the Lights for Clearance and Stability
Common locations include crash bars, fork mounts, headlight brackets, and handlebars. Whatever you choose, verify full steering lock-to-lock and full suspension compression — nothing should contact the lights, brackets, or wiring. Stay clear of exhaust headers, the radiator fan, and any hot or rotating parts.
Mount the pods loosely at first. Use the provided brackets and hardware, and apply a dab of medium-strength thread locker to the bolts. Leave the fasteners just snug enough to hold position so you can rotate the pods during final aiming. If the pod uses a lens with internal flutes that control the beam pattern, keep the lens vertical — rotating the housing without rotating the lens distorts the beam.
Wiring a Fused, Relay-Controlled Circuit
Run a fused positive lead as close to the battery as possible — the fuse protects the whole circuit, so placing it at the battery terminal means the wire past the fuse is covered. Connect ground to the battery negative post or a clean chassis ground point.
Use a relay to handle switching. The relay’s trigger wire (usually white, sometimes yellow for low-intensity) connects to a verified switched 12V source — a circuit that only has power when the ignition is on. Never tap a constant-hot wire; the lights would stay on and drain the battery. If your kit supports high-beam activation, the blue trigger wire connects to the high-beam circuit. Verify every source with a multimeter or test light before crimping.
If you’re still choosing lights for your build, check out our roundup of the best motorcycle auxiliary lights for reliable options that fit different bike styles and budgets.
Use waterproof connectors, heat-shrink tubing (slide it on before crimping — forgetting is a common mistake), and zip ties to secure the harness. Keep wiring away from sharp edges, the exhaust, the radiator fan, and any steering or suspension travel. Cap any unused trigger wires to prevent shorts.
| Component | Spec / Value |
|---|---|
| M8 mounting bolt torque | 13.5 ft-lbs (18 Nm) |
| M3 lens screw torque | 10 in-lbs (1 Nm) |
| Aiming distance from wall | 25 ft |
| Aim line below pod center | 2 in |
| Fuse location | As close to battery as possible |
| Trigger source | Switched 12V only, verified with meter |
Aiming the Beams and Finishing the Install
Reconnect the battery and test the lights before full reassembly. Verify both low and high functions if your kit uses dual-intensity. Place the bike 25 feet from a flat wall with a rider seated in normal posture. Mark a horizontal line on the wall 2 inches lower than the center of each pod, then aim the hotspot of each beam to that line. This gives useful light down the road without blinding oncoming traffic.
Take the bike for a short ride to let vibration settle the hardware, then retorque all mounting bolts to the values above. Inspect the wiring for any signs of chafing, stretching, or heat — especially near the exhaust and steering stops.
FAQs
Do I need a relay for auxiliary motorcycle lights?
Yes. A relay lets the lights draw power directly from the battery while using a low-current trigger from a switch or OEM circuit. Without a relay, the full current runs through the switch, which creates voltage drop and risks melting the wiring over time.
Can I wire auxiliary lights to the high-beam circuit?
If your kit supports it, yes. The high-beam trigger wire (often blue) connects to the positive side of the high-beam bulb or harness. This makes the aux lights activate only when the high beams are on — common for setups that need extra road light without dazzling traffic during low-beam riding.
What happens if I tap a constant-hot wire instead of a switched source?
The lights stay on whenever the battery is connected, even with the ignition off. That drains the battery and can overheat the LEDs or wiring if left on. Always verify your trigger source is switched using a multimeter or test light before making connections.
References & Sources
- Dennis Kirk. “How to Install Auxiliary Lights on a Motorcycle.” Covers mounting, wiring, torque specs, and aiming procedure.