Kenworth K220 front and rear turn signal bulbs utilize 1157 and 1156 sizes, with the front requiring the 1157 bulb size exclusively. The replacement chart covers 1988 to 1994 production years and documents bulb size specifications for turn signal applications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 1157 bulb is the most frequently specified type across the Kenworth K220 turn signal data, appearing in both front and rear positions across multiple model years.
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, and classified under the ANSI standard used in the US and Canada.
The 1156 bulb is a single-filament type operating at 12V at 21W, fitted with a BA15s bayonet base, and also carries ANSI classification for the US and Canadian markets.
The BAY15d base of the 1157 and the BA15s base of the 1156 are physically distinct bayonet fittings, which means the two bulb types are not interchangeable despite sharing the same 12V operating voltage and 21W primary wattage rating.
The front turn signal position on the Kenworth K220 uses the 1157 bulb uniformly across all listed years from 1988-1994, with no variation in that position throughout the specification range.
The rear turn signal position shows a split between the two bulb types: the 1156 is specified for the 1988 and 1990 model years, while the 1157 is specified for 1989 and 1991-1994.
Because the rear turn signal alternates between the 1156 and 1157 across certain model years, year-specific verification is particularly relevant for that position on the K220.
The dual-filament design of the 1157 allows it to serve both a high-intensity turn signal function and a lower-intensity parking or running light function within a single bulb housing, which is a functional distinction from the single-filament 1156.