Acura RL Headlight Bulb Size

Additional Notes

• The Acura RL uses three distinct high beam bulb types across its production span: the 9003, H1, and 9005. The 9003 is a dual-filament halogen bulb operating at 12V with a 60W/55W rating and a P43t base, built to the ANSI standard used in the US and Canada. The H1 is a single-filament halogen bulb rated at 12V and 55W with a P14.5s base, conforming to the ECE standard recognized in Europe, the US, and Japan. The 9005 is also a single-filament halogen bulb but carries a higher 65W output, uses a P20d base, and follows the ANSI standard.
• The 9003 served as both the high beam and low beam bulb in the Acura RL for the 1996-1998 model years, functioning as a dual-filament unit within a single housing. From 1999 onward, the high beam and low beam functions were split into separate, dedicated bulbs, each with its own socket type and wattage rating.
• The low beam circuit in the Acura RL transitioned to HID (high-intensity discharge) xenon technology beginning with the 1999 model year. HID bulbs operate on a fundamentally different principle than halogen bulbs, producing light through an electrical arc between two electrodes within a xenon gas-filled capsule rather than through a heated tungsten filament.
• Two HID bulb types are specified for the RL low beam: the D2R for 1999-2004 and the D2S for 2005-2012. Both operate at 85V and 35W and share the same ECE standard classification, but they are not interchangeable. The D2R carries a P32d-3 base and is designed for reflector-type housings, while the D2S uses a P32d-2 base and is intended for projector-type housings. Installing the wrong type can result in improper light distribution and glare.
• Both the D2R and D2S bulbs require an external ignitor to initiate the high-voltage arc needed to strike the xenon discharge. This ignitor is a separate component from the ballast and is not present in halogen headlight systems, making HID and halogen assemblies electrically incompatible without significant modification.
• The high beam bulb changed from the H1 to the 9005 between the 2004 and 2005 model years. These two bulbs differ in base type, P14.5s versus P20d respectively, meaning they are physically non-interchangeable despite both being single-filament 12V halogen bulbs. The 9005 also draws 65W compared to the H1's 55W.
• The H1 bulb, used in the RL high beam circuit for 1999-2004, holds approval under both ECE and US regulations, giving it broader geographic certification than the ANSI-exclusive 9005 that replaced it. This distinction is relevant when sourcing replacement bulbs, as ECE-certified bulbs are subject to different photometric testing criteria than ANSI-certified ones.
• The 9003 bulb, specified for the 1996-1998 RL, is rated at 60W on the high beam filament and 55W on the low beam filament within the same envelope. Its P43t base is a bayonet-style fitting common to dual-filament halogen bulbs and is not compatible with the single-filament sockets used in later RL model years.