Prevost Shell Headlight Bulb Size

Additional Notes

• The H9 bulb is the most widely specified type across the Prevost Shell headlight data, covering both high beam and low beam positions from 2006-2019. It is a single-filament halogen bulb rated at 65 watts, operating on a PGJ19-5 base, and is designed for high-intensity focused beam output rather than dual-function use.
• For low beam positions on 2006-2019 models equipped with HID headlamps, the D2S bulb is specified as an alternative to the H9. The D2S is a high-intensity discharge bulb that operates through an arc discharge between two electrodes rather than a heated filament, and it requires a compatible ballast and igniter already integrated into the HID headlamp assembly.
• Because the H9 and D2S serve the same low beam position on 2006-2019 Prevost Shell vehicles, fitment is determined strictly by the headlamp system installed. The two bulb types are not interchangeable, as they differ in operating principle, base type, and required supporting hardware.
• The 9004 bulb is specified for both high beam and low beam positions on 1990-2004 models. Unlike the H9, the 9004 is a dual-filament bulb, meaning a single unit serves both beam functions. Its connector uses a three-prong configuration that is not compatible with single-filament sockets.
• The 1990 high beam position lists both the 9004 and the H4651 as specified bulb sizes, indicating that two distinct headlamp configurations were in use during that model year. These two bulb types are not interchangeable due to differences in base design and housing fitment.
• The H4651 and H4656 are sealed-beam rectangular halogen bulbs specified for 1984-1990 high beam positions. The H4651 produces a high beam pattern, while the H4656 is associated with a low beam pattern, reflecting the era's practice of using separate dedicated sealed-beam units for each function.
• For the 1984-1989 model years, both the H4651 and H4656 are listed together under the high beam sub-part, while the H4656 alone covers the low beam sub-part for the same years. This indicates a multi-lamp sealed-beam arrangement where individual units handled distinct beam patterns within the same headlamp cluster.
• Sealed-beam bulbs such as the H4651 and H4656 integrate the filament, reflector, and lens into a single sealed unit. This construction means the entire assembly is replaced as one piece, unlike the replaceable-capsule design used by the H9 and D2S in later model years.
• The transition from sealed-beam H4651 and H4656 bulbs to the dual-filament 9004 occurred between the 1990 and 1991 model years for the low beam position, with the 1990 high beam position representing an overlap year where both bulb generations are listed.
• The shift from the 9004 dual-filament bulb to the single-filament H9 took place between the 2004 and 2006 model years, coinciding with the introduction of the D2S HID option for low beam applications on the Prevost Shell.