Modding NB side markers for light

[— Agent☣Orange —]

The NB Miata does not come with rear parking/running lights but uses a reflector instead. However, it is easy to add them and there are a couple options available. One way is to create simple parking/running lights that simply turn on when the light switch is on and the other is to have rear parking/running lights that flash alternatively with the turn signal. This writeup covers the simple, parking/running light addition.

In a nutshell, all you're doing is tapping into the existing parking/running light wiring and adding a bulb to each side marker. The NB comes from the factory with reflectors but you can tell from the housing, it was designed to hold a light but just never drilled out that way. Lame, Mazda, lame...
Here is a comparison between the NA and NB rear side markers. The NA is already cut out for a light but the NB is not although it can be.



The easiest thing you can do is buy a set of used NA rear side markers like these but if you're good with a Dremmel and a routing bit, you can do this for no cost. In this case, I already had a spare set of NA rears.



The next thing you'll need is a dongle for each lens. Since exact-fit NA dongles are really part of the existing wiring harness and not something you can just buy, it's easier to get a set of these from the local auto parts store. They're supposed to be for GM but they'll work.




All that's important is that they're a four-pronged design that holds a type 194 bulb. Application note: At this point you can choose a nicer LED bulb without causing any hyperblink or cruise control issues since you are adding these bulbs, not replacing.


If you are Dremmeling out your own NB lenses, you'll want to custom cut them out to match the dongles. If you're using NA lenses, you will have to cut the tabs on the dongles to match the stock NA lens opening since they are a bit too wide. This is pretty easy to do with a box cutter on the workbench.



Now you'll want to tap into the existing wiring using these T-taps from Radio Shack. These fit 18-14 gauge Miata wiring and are superior to the old vampire taps.



You will need to remove the rear reflectors which are obviously held on via two Philips screws each and then pull out the tail light assembly. The assembly is accessed by first removing the rearmost carpeted trim panel in the trunk held on by plastic snaps. Be careful because these snaps can not only be old and brittle but it is easy to miss the one under the trunk latch. Then the driver side plastic cubby has to be removed via a single Philips screw.









Next, you have to remove each tail light by first unscrewing the Philips screw on top and then two 10mm nuts inside. Pull the assembly straight out by wiggling up and down slightly to dislodge. *When reassembling afterward, do not over tighten.





Using a 12V test light, isolate the positive wire to the stock parking/running light bulb. In this case, it is the white wire.

[— Agent☣Orange —]

At this point, you can build your harness on the workbench by guessing how much wire you'll need which is physically easier or you can custom cut lengths of wire on the car itself. In this example, each dongle came with several inches of wire so I only had to use a few inches more to complete the run. You can reach in between the bumper and frame to grab the wiring from the side marker location; no getting under the car required.







Next, tap into the white wire using the T-tap



And then ground the other wire. You can ground anywhere on the metal frame so I chose to use a couple eye connectors, drill a small hole behind each tail light and screw them in with self-tapping screws. Ground is solid and pretty much away from direct moisture which can corrode the connection.




At the side marker end, make sure to shrink wrap your splices because this area gets splashed with lots of water.





Before buttoning everything back up, ensure your wiring is correct and everything lights up as planned



and in this case, we're looking pretty good