Prevost High Decker Headlight Bulb Size

Additional Notes

• The H9 bulb is the most widely specified type across the Prevost High Decker headlight data, appearing in both high beam and low beam positions for model years 2005-2019. It is a halogen bulb operating at 65 watts with a PGJ19-5 base, designed for single-filament use in projector or reflector housings.
• The 9004 bulb type is specified for both high beam and low beam positions on the Prevost High Decker from 1990-2003. It is a dual-filament halogen bulb with an HB1 designation, meaning a single unit handles both beam functions through two separate filaments within one envelope.
• Because the 9004 bulb serves both high and low beam functions through its dual-filament construction, it is not interchangeable with the H9, which is a single-filament bulb. Substituting one for the other would result in incorrect or non-functional beam output.
• For model years 2005-2019, the Prevost High Decker low beam position accommodates two distinct bulb types depending on headlamp system: the H9 for halogen capsule headlamps and the D2S for HID headlamps. These two systems are not interchangeable, as HID and halogen technologies require different ballasts and housing configurations.
• The D2S is a high-intensity discharge bulb that operates through an electrical arc between two electrodes rather than a heated filament. It requires a compatible HID ballast and igniter, making it incompatible with standard halogen wiring without additional components.
• The 1990 Prevost High Decker high beam position lists two bulb sizes: the 9004 and the H4651. This indicates that two different headlamp configurations were available for that model year, each requiring a different bulb.
• The H4651 and H4656 bulb types appear in the 1988-1990 high beam data and the 1988-1989 low beam data. Both are sealed-beam rectangular halogen units, a format that was common before the widespread adoption of replaceable-bulb composite headlamp assemblies.
• The H4651 and H4656 differ in their light output characteristics, with the H4656 typically used for low beam and the H4651 for high beam applications. The 1988-1989 specifications reflect this split, listing H4656 for low beam and both H4656 and H4651 for high beam in those years.
• The high beam position for model years 2005-2019 specifies only the H9, with no HID variant listed, unlike the low beam position for the same years. This means the high beam circuit on those vehicles is halogen-only regardless of whether the low beam system is halogen or HID.
• The absence of a 2004 and 2009 entry across all positions in the specifications means no bulb data is attributed to those model years for the Prevost High Decker in this dataset.