The Acura RDX back up light utilizes bulb sizes 921 and 7440 for the rear illumination components. Data for the specific lighting requirements covers the range from 2007 through 2018.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Acura RDX back up light specifications list two bulb types across its model years: the 921 and the 7440, both of which conform to ANSI standards recognized in the United States and Canada.
The 921 is a T15 wedge bulb rated at 12 volts and 16 watts, while the 7440 is a T20 single-filament wedge bulb rated at 12 volts and 21 watts, making the 7440 a higher-wattage unit despite sharing the same operating voltage.
The T15 and T20 designations refer to the tubular bulb body size, with T20 being physically larger than T15. These two types are not interchangeable due to differences in body size and wattage.
The Acura RDX used the 7440 bulb for the back up light across the 2007-2012 model years.
Starting with the 2013 model year, the Acura RDX transitioned to the 921 bulb for the back up light, a fitment that continued through the 2018 model year.
The 921 and 7440 are both wedge-base bulbs, meaning they use a plastic wedge base rather than a metal screw or bayonet base, but their wedge sizes differ and the two types do not share a common socket fitment.
The 2017-2018 Acura RDX specifications also include an Outer Back Up Light position, which uses the 921 bulb, consistent with the standard back up light fitment for those same years.