HID Projector Retrofit for the 7th-Gen Honda Accord Headlight

Decide on a projector-based system rather than a bare reflector conversion so the finished beam has a sharp, controllable cut-off. Acura TSX projectors are a common choice because they throw a wide pattern and are straightforward to work with, and each unit already has four mounting holes to anchor it inside the housing. Source a matched pair, along with an HID ballast, ignitor, and bulb set. Buy from used-parts listings patiently to find a fair price; the original builder paid roughly $117 for the projectors and about $150 for a ballast, ignitor, and bulb set. Lay all components out and confirm the set is complete before touching the car.

The ballast is the most important part of the system because it meters the current feeding the bulb and must hold that current steady to reach the bulb's rated life of around 2000 hours. For this reason prefer an OEM ballast over a generic aftermarket unit. The ignitor is the small lead ending in a metal cap that fires the high-voltage pulse to strike the arc; if it is a separate piece rather than built into the ballast, keep it paired with its ballast. HID output is dramatically higher than the stock halogen: roughly 3300 lumens versus about 1200 from the original bulb.

OEM HID bulbs come in two main types. D2R bulbs are designed for reflector housings (as found in some Prius, Lexus, Infiniti, and older Acura models) and carry a ceramic coating on part of the glass to suppress glare, which costs roughly 200-300 lumens. D2S bulbs are designed for projectors. If your kit came with D2R bulbs, they can still be used in a projector: file down the locating notches at the base of the bulb so it seats into the projector's bulb holder. Remove only enough material for a clean fit.

Each ballast has two connections: an input that accepts power and an output that feeds the bulb. OEM ballasts are frequently sold without the input pigtail, so confirm you have the correct power cord for your ballast or buy a matching pair separately. Attach the pigtail to the ballast's power-input port so you have clean leads to join to the vehicle-side wiring in the next step.

Rather than tapping the factory headlight circuit, run a dedicated relay harness fed directly from the battery so the HID load is isolated from the car's original wiring and cannot overload it. Crimp the ballast pigtail leads to the positive and negative wires of the harness, matching polarity. This separate circuit is inexpensive insurance against damaging the vehicle's electrical system. Secure and insulate every joint before powering anything up.

Work on a spare set of headlights so the car remains usable and so a mistake does not leave it off the road. Soften the factory sealant that bonds the lens to the housing with a heat gun, moving steadily around the seam; a low oven is an alternative for warming the whole assembly. Once the adhesive is pliable, carefully separate the lens from the housing so you can access the interior for mounting the projector. Work slowly at the corners, where the housing plastic and the internal reflector parts are easiest to crack.

Position each projector using its four mounting holes and anchor it with L-brackets, machine screws and nuts, and #8 flat and locking washers, trimming and test-fitting until the optic sits level and centered for a correct beam. Use metal shears and the Dremel to cut brackets and clearance as needed. Build a shroud around each projector to hide the raw hardware and tidy the cut-off: a 2 inch inner-diameter flange makes the collar, and chrome range catch pans (or, as several builders in the thread did, a polished beer can or a garden-lamp reflector) provide the decorative cover. Dry-fit everything before bonding.

Once the projectors and shrouds are secured, bond and seal the joints with JB Weld and reheat the housing sealant to close the lens back onto the housing, checking for a fully sealed perimeter to keep moisture out. Reinstall the headlights, connect the relay harness, and power up. Aim the beams carefully against a wall or with the car level on flat ground: a projector's advantage is its sharp cut-off, so a few degrees of error will either blind oncoming drivers or waste the pattern on the ground. Adjust each side until the cut-off sits at the correct height and the two beams match.