How to Wire an NB2 Headlight Conversion on Your Mazda Miata
How to Wire an NB2 Headlight Conversion on a Mazda Miata
Swapping the sleek NB2 projector headlights onto an earlier NB1 Miata modernizes the front end, but the factory wiring harnesses do not mate up. Doing this DIY correctly prevents electrical shorts and ensures proper light output.
The Short Answer (TL;DR)
Converting to NB2 headlights on your Mazda Miata takes about two hours and requires splicing the high and low beam circuits. The NB1 uses a single H4 bulb, while the NB2 uses separate HB3 and HB4 bulbs. You must cut the factory H4 pigtail, wire in the new connectors, and ensure proper grounding. Upgrading your intake or radiator while the bumper is off is highly recommended.
The DIY Process Overview
To complete the NB2 headlight conversion, you will need wire strippers, heat shrink tubing, soldering gear or waterproof butt connectors, and the NB2 headlight pigtails. First, disconnect the negative battery terminal to prevent shorting the lighting circuit. Remove the front bumper cover to gain full access to the headlight mounting brackets and factory wiring.
Cut the factory H4 connector off the NB1 harness, leaving enough wire to work with. The H4 harness has three wires: ground, low beam power, and high beam power. You must split the factory ground wire to feed both the new HB3 (high beam) and HB4 (low beam) connectors. Splice the low beam power to the HB4 pigtail and the high beam power to the HB3 pigtail, then seal all connections with heat shrink.
Why You Should Upgrade While You're In There
Removing the front bumper on an NB Miata gives you unobstructed access to the front core support. Since you already have the car taken apart, it is the perfect time to install an aftermarket cold air intake or upgrade the factory radiator. Routing intake piping is significantly easier without the bumper cover in the way.
Recommended Upgrade: Cold Air Intake System
Frequently Asked Questions
Do I need to upgrade the fuses for NB2 headlights?
No. The factory NB1 headlight fuses and relays are rated to handle the amperage of the standard NB2 halogen bulbs. If you are installing high-draw aftermarket ballasts or HID kits, a dedicated relay harness wired directly to the battery is required.
Will the high beams and low beams stay on at the same time?
With standard NB1 factory wiring, the low beam turns off when the high beam is activated. To keep both illuminated for maximum visibility, you will need to wire a custom diode or relay into the steering column switch block.
