Alfa Romeo Giulia high beam and low beam headlight bulbs utilize D3S and D5S size specifications. The replacement chart covers vehicle production spanning 2017 to 2023.
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 D3S and D5S bulb types appear across all listed model years of the Alfa Romeo Giulia, covering both high beam and low beam positions in every case where HID headlamps are fitted.
The D3S is an ECE-standard, mercury-free HID xenon discharge bulb rated at 42V and 35W, featuring a PK32d-5 base with an integral ignitor built into the bulb body. Its design is specific to projector-type housings.
The D5S is an ECE-standard HID xenon discharge bulb of the low-voltage compact type, rated at 12V and 25W, and uses a PK32d-7 base. The 25W power rating corresponds directly to the "25W HID Headlamps" qualifier noted in the specifications for 2017-2020 fitments.
The PK32d-5 base of the D3S and the PK32d-7 base of the D5S are physically distinct and electrically incompatible. These two bulb types are not interchangeable with each other despite both being HID xenon discharge types.
For the 2022-2023 Giulia, the D3S is the sole specified bulb for both high and low beam positions across all HID-equipped variants, with no D5S fitment listed for those years.
For the 2021 Giulia, the D5S is the sole specified bulb for both beam positions, representing a single-year configuration distinct from the dual-option fitments of earlier years.
The 2017-2020 Giulia carries two separate HID specifications per beam position: the D5S for headlamps designated as 25W HID, and the D3S for headlamps designated without that wattage qualifier. These represent different factory headlamp assemblies requiring different bulbs.
Because the D3S incorporates an integral ignitor, it does not require a separate external ignitor unit, whereas the D5S, as a low-voltage compact type, operates within a different ballast and ignition architecture suited to its 12V system voltage.