Kenworth K300 front turn signal bulbs use 1157 size, while rear turn signal bulbs use P21W or 1157 size. The replacement chart covers 1993 to 1997 vehicle 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 Kenworth K300 uses two distinct bulb standards across its front and rear turn signal positions: the ANSI-standard 1157 and the ECE-standard P21W.
The 1157 is a dual-filament bulb operating at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base.
The P21W is a single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base, and follows ECE regulations common in European and worldwide markets.
The BAY15d base of the 1157 and the BA15s base of the P21W are not interchangeable, as the offset pins on a BAY15d base differ from the single-pin configuration of a BA15s base.
The front turn signal position on the Kenworth K300 uses the 1157 bulb consistently across the 1993-1997 model years.
The rear turn signal position on the Kenworth K300 (1993-1997) does not follow the same consistency as the front, with the 1996 model year specifying the 1157 rather than the P21W used in the other years.
Because the 1157 carries a dual filament and the P21W carries only a single filament, substituting one for the other in a rear turn signal circuit may affect how the socket and wiring interact with the bulb's electrical load.
The 1996 rear turn signal specification for the Kenworth K300 calls for the 1157, which differs from the P21W specified for the 1993-1995 and 1997 model years, making year-specific verification necessary before replacement.