Kenworth T300 front turn signal bulbs use 1157 size while rear turn signal bulbs use 1156 size. The replacement chart covers 1995 to 1997 vehicle production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Kenworth T300 uses two distinct bulb types across its front and rear turn signal positions for the 1995-1997 model years: the 1157 at the front and the 1156 at the rear.
The 1157 is a dual-filament bulb, meaning it carries two separate filaments within a single envelope, allowing it to serve more than one lighting function simultaneously, such as turn signaling and parking illumination.
The 1157 operates on a 12-volt circuit and draws 21 watts on its primary filament and 5 watts on its secondary filament, reflecting its dual-purpose design.
The 1157 uses a BAY15d bayonet base, which features two offset pins positioned at different heights to prevent incorrect insertion and ensure proper filament orientation.
The 1156 is a single-filament bulb, dedicated to one lighting function, and draws 21 watts on its sole filament at 12 volts.
The 1156 uses a BA15s bayonet base, which has two pins at the same height, distinguishing it physically from the BAY15d base of the 1157.
Because the 1157 and 1156 share the same 15mm bayonet base collar width but differ in pin alignment, the two bulbs are not interchangeable despite their similar appearance.
Both the 1157 and 1156 conform to ANSI standards recognized in the United States and Canada, indicating standardized electrical and physical specifications across manufacturers.