The IS300 Sportcross trunk has only a small light, and it’s positioned to one side instead of overhead, so I always wanted to add more lighting. At the same time, I was missing one of my access panels on the inside of the hatch, so to solve both problems I embedded new trunk interior lights in 3D-print housings that take the place of the access panels. They also illuminate the area behind the car when the hatch is open.
I designed a custom 3D-printed housing around these 12V LEDs from Harbor Freight. I started the housing design by tracing the existing access panel on my iPad screen, then pasted that as an image into a CAD file. Then I used splines to match the tracing and generate solid geometry. It took several iterations to tune in the geometry, especially for the snap-fit features, fitting up 3D-prints on the car and making note of where adjustments were needed.
The trunk side light gets powered by the Body ECU when the hatch is open, but the light panel includes a switch that can turn the light off while the trunk is open. I wanted to control the hatch lights the same way but was concerned that the small switch could not handle the additional current needed to power the additional LEDs directly. Instead of directly switching the LEDs from that switch, I powered the LEDs from the same wiring that feeds the side light (that’s controlled by the Body ECU), and I installed a separate relay for the switch to control. I ensured the total power draw was lower than the fuse rating for the power-feed circuit (after switching the side lamp to an LED panel), and the switch now handles less current than before.
I ran the new wiring up behind the D-pillar trim, above the headliner, and through the rubber boot to the hatch. I took the opportunity to fish through additional wires so I would not have to mess with this again. I also ran a USB extension cable to the hatch from the right side of the trunk to connect the external microphone for my Mobile BirdNET project.
I connectorized the LED lights with some SAE connectors so the panels could be removed if needed.
As mentioned above, I replaced the side light bulb with an LED panel to increase the brightness and match the color of the new lights. The map light and dome light got the same treatment.
