The Acura CL front turn signal bulb accommodates 1157NA and 7440 sizes, while the rear turn signal bulb uses 7440 and 3496 sizes. The replacement chart covers 1997 through 2003 model years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 1157NA is a dual-filament bulb rated at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base. Its natural amber glass produces a yellow-orange light output without requiring a colored lens or external filter.
The 7440 is a single-filament wedge bulb in the T20 form factor, rated at 12V and 21W. Unlike the 1157NA, it has no secondary filament, making it unsuitable as a direct substitute in sockets designed for dual-filament operation.
The 3496 is a dual-filament bulb sharing the BAY15d bayonet base with the 1157 family, rated at 12V. Its physical base type is the same as the 1157NA, though the two are distinct part numbers and are not listed interchangeably in these specifications.
For the Acura CL, the front turn signal shifted from the 7440 in 1997-1999 to the 1157NA in 2001-2003, representing a change from a single-filament wedge fitment to a dual-filament bayonet fitment across those model year groups.
The rear turn signal on the Acura CL followed the opposite pattern, using the 3496 in 1997-1999 and transitioning to the 7440 in 2001-2003, moving from a dual-filament bayonet base to a single-filament wedge base.
Because the front and rear positions use different base types within the same model year, the front and rear turn signal bulbs for the 2001-2003 CL are not interchangeable with each other despite both being 12V, 21W-rated components.
For the 1997-1999 CL, the rear turn signal uses the 3496, which shares its BAY15d base with the 1157 family. However, substituting an 1157 or 1157NA in that socket would require confirming voltage and wattage compatibility beyond base type alone.
All three bulb types listed across these specifications conform to ANSI standards applicable in both the United States and Canada, indicating a standardized electrical and physical specification rather than a proprietary fitment.
The 7440 wedge base and the BAY15d bayonet base are mechanically incompatible socket types. A vehicle position specifying one cannot physically accept the other without modification to the socket housing.
The 1157NA's natural amber glass is a distinguishing characteristic from a standard 1157, which uses clear glass. In applications where the lens housing is also clear, the 1157NA provides the amber signal color through the bulb itself rather than through the lens.