Buick Cascada front turn signal bulbs use 7443NA size while rear turn signal bulbs use 12496 or PY21W size. The replacement bulb size chart covers 2016 to 2019 model years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Buick Cascada front turn signal uses the 7443NA bulb across all model years covered in the specifications, spanning 2016-2019.
The 7443NA is a dual-filament T20 wedge bulb rated at 12V with a 21W main filament and a 5W secondary filament, conforming to ANSI standards used in the United States and Canada.
The natural amber glass of the 7443NA produces its amber signal color through the glass itself rather than through a colored lens or housing, which is a defining characteristic of the NA designation.
The rear turn signal of the Cascada uses the 12496 for 2016, 2017, and 2019, while the 2018 model year uses the PY21W instead.
The 12496 is a Philips/Osram proprietary part number for a 12V halogen bulb intended for specialty automotive applications, meaning it is not a universal ANSI or ECE standard type.
The PY21W conforms to ECE standards, which are used in European and international markets, and features a BAU15s offset bayonet base rated at 12V and 21W with a single filament.
The BAU15s base of the PY21W has an offset pin configuration that physically prevents it from being inserted into sockets designed for the more common BA15s base, making it non-interchangeable with standard single-filament bayonet bulbs.
The front and rear turn signal bulbs on the Cascada are not interchangeable with each other, as the front uses a wedge base (T20) while the rear uses either a proprietary halogen type or a bayonet base format depending on the model year.
The divergence in rear turn signal bulb type between the 2018 model year and the surrounding years indicates that the 2018 Cascada rear turn signal socket is not compatible with the 12496 used in the other years without a corresponding housing or socket difference.