The Kenworth K100 front and rear turn signal bulbs utilize a 1157 size, with rear applications also accepting 1156 bulb options. The replacement chart covers vehicle production spanning 1981 to 1985.
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 dominant type across the Kenworth K100 turn signal specifications, appearing in both front and rear positions for the majority of model years covered.
The 1157 is a dual-filament bulb operating at 12 volts, with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base.
The BAY15d base features two offset pins, which physically prevents it from being interchanged with single-filament bulbs that use a different base configuration.
The 1156 is a single-filament bulb operating at 12 volts at 21W, mounted on a BA15s bayonet base with a single locating pin.
Both the 1157 and 1156 are ANSI-standardized bulbs recognized across the United States and Canada, meaning they conform to a defined set of electrical and physical specifications.
The Kenworth K100 rear turn signal for the 1984 model year takes a 1156 bulb, while all other listed model years from 1981-1985 use a 1157 in that same position.
Because the 1156 and 1157 share a similar physical size but differ in base type and filament count, the two bulbs are not interchangeable despite their close numerical designation.
The front turn signal position on the Kenworth K100 uses the 1157 bulb uniformly across all listed model years from 1981-1985.