The Buick Cascada high beam headlight uses D3S or H7 bulb sizes, while the low beam headlight requires a D3S bulb size. The replacement chart covers 2016 through 2019 production 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.
ECE standard (Europe & worldwide). Mercury-free HID (xenon) discharge bulb with PK32d-5 base and integral ignitor, for projector-type housings. 42V, 35W.
The Buick Cascada high beam headlight accepts two distinct bulb types across its 2016-2019 model years: the D3S for HID-equipped vehicles and the H7 for vehicles fitted with halogen capsule headlamps.
The D3S is a high-intensity discharge bulb that operates without an internal filament, instead producing light through an electrical arc between two tungsten electrodes within a xenon gas-filled quartz capsule.
The H7 is a single-filament halogen bulb operating on a PX26d base, commonly used in projector and reflector housings where a dedicated high beam source is required.
The low beam headlight position on the Cascada uses the D3S exclusively across all four model years, with no halogen alternative listed for that position.
The D3S designation indicates a discharge bulb with a three-pin base and an integrated igniter, distinguishing it from the D3R variant, which carries a coated bulb for use in reflector housings rather than projector housings.
Because the high beam position on the Cascada accommodates either D3S or H7 depending on the headlamp system installed, the two bulb types are not interchangeable with each other, as they operate on fundamentally different electrical and optical principles.
HID systems require a ballast to regulate the high-voltage arc that powers a D3S bulb, meaning the D3S cannot function as a direct replacement in a vehicle wired solely for halogen operation without additional components.
The H7 fitment is conditional, applying only to Cascada units built with halogen capsule headlamps, a distinction that must be confirmed before a replacement bulb is selected for the high beam position.