The Prevost High Decker front turn signal requires a 3057 bulb size while the rear turn signal uses a 1156 bulb size. Replacement chart data covers 1990 to 2004 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.
The Prevost High Decker uses the 3057 bulb for the front turn signal across all documented model years from 1990 to 2004.
The 3057 is a dual-filament T25 wedge bulb rated at 12V with a 27W high filament and a 7W low filament, conforming to ANSI standards recognized in both the United States and Canada.
Its dual-filament design allows a single bulb to serve two distinct brightness levels, which is typical in applications where the same lamp housing handles both turn signal and parking light functions.
The rear turn signal on the Prevost High Decker uses the 1156 bulb for model years 2000-2003.
The 1156 is a single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base, and also conforms to ANSI standards for the US and Canadian markets.
The BA15s bayonet base of the 1156 is a single-contact fitting, which is not interchangeable with dual-contact bayonet bases such as the BA15d used on some other automotive bulbs.
The front and rear turn signal positions on the Prevost High Decker use different bulb types, meaning the 3057 and 1156 are not interchangeable between positions despite both operating at 12V.
The 3057 wedge base and the 1156 BA15s bayonet base are physically incompatible socket types, reinforcing that substitution between the two positions is not possible without socket modification.