OEM Acura TL HID (D2R) Conversion for JDM H4H Headlamps

Obtain a complete factory HID kit from a 1999 Acura TL: both Matsushita ballasts/igniters and the D2R bulbs. Use D2R, not D2S - the D2R has a light-blocking stripe painted on the capsule for reflector housings, which the D2S lacks. OEM D2R and D2S bulbs are common at dealers and on eBay, so replacements are cheap and not brand-specific.

This is the most time-consuming part. Grind off the three tabs on the bulb base, then grind a small rounded slit at the 3 o'clock position as viewed from the back of the bulb. This slit aligns and seats the bulb in the H4H socket. Do not worry about the bulb falling through the housing - the large D2R/D2S plug on the back stops it from going in too far. For orientation, the small rod on the bulb aligns at the bottom.

Reuse the headlamp's rubber bulb seals rather than discarding them - cut a slit in each seal just large enough to push the D2R plug and wiring through. Ideally, devise a way to fully reseal the rubber around the wiring afterward, since the slit compromises the weather seal (the original author was not satisfied leaving it unsealed).

The stock H4H wire retaining clip will not capture the modified bulb, so form a replica clip from stiff wire. The original was bent from a paperclip, but that proved weak - use something thicker. Bend the rear section into a V shape so it presses the bulb forward into the socket when clipped in. To swap clips, unscrew the original clip's anchor screw just far enough to wiggle the old clip out, then fit the fabricated clip the same way. It mounts and latches exactly like the original.

Do the wiring properly with solder and heat shrink tubing rather than crimps or twists. Solder a standard H4/sealed-beam harness pigtail (sold at any auto parts store) directly to the ballast input wires so the kit becomes plug-and-play. Fit male-to-male brass connectors to the pigtail so it mates with the car's factory headlight plug. A good soldered joint will never vibrate apart.

Fit each modified D2R bulb into its H4H socket with the alignment rod at the bottom, secure it with the fabricated retention clip, and pass the plug through the slit rubber seal. Connect the ballast harness to the car's factory plug, wrap the H4 pigtail connections in electrical tape to secure them, and zip-tie the two connector plugs face-to-face so they cannot shake loose (a practice recommended by HID kit maker McCulloch). Mount the ballasts securely in the engine bay - zip ties will do temporarily, but plan a proper permanent mounting.

The JDM housing has no glare shield, so there is no distinct projector-style cutoff line. Aim the headlamps down - when the author previously ran an H4 HID kit in these housings, aiming them fully down helped tremendously. Verify against a wall and on the road that the beam stays on the pavement and does not light up signs, houses, or oncoming traffic. To further reduce upward stray light, the underside of the reflector bowl can be painted black or flat grey, since the upward glare comes mainly from the bottom of the housing.