Kenworth K100E front turn signal bulbs use 1157 size while rear turn signal bulbs use 1156 or 1157 size. The replacement chart covers vehicle production years spanning 1985 to 1997.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Kenworth K100E front turn signal position uses the 1157 bulb across all listed model years from 1985 to 1997, indicating a consistent fitment requirement for that position throughout the entire production span covered by these specifications.
The 1157 is a dual-filament bulb operating at 12V with a 21W/5W output rating and a BAY15d bayonet base, conforming to ANSI standards recognized in both the United States and Canada.
The dual-filament design of the 1157 allows it to serve two lighting functions within a single housing, which is why it is suited to front turn signal positions that may also require a running light function.
The rear turn signal position on the Kenworth K100E uses the 1156 bulb for most listed years, including 1985-1990, 1992-1995, and 1997.
The 1156 is a single-filament bulb operating at 12V with a 21W output rating and a BA15s bayonet base, also conforming to ANSI standards recognized in both the United States and Canada.
The BA15s base of the 1156 and the BAY15d base of the 1157 are physically distinct, as the BAY15d features offset locating pins to prevent incorrect installation. The two bulbs are not interchangeable despite their similar appearance.
The Kenworth K100E rear turn signal position calls for the 1157 in 1991 and 1996, rather than the 1156 used in surrounding years, indicating that those two model years require a dual-filament bulb at the rear instead of a single-filament one.
Installing a 1156 in a socket designed for a 1157 is not possible without modification, due to the differing pin configurations of the BA15s and BAY15d bases.
Both the 1156 and 1157 operate on a 12V electrical system, which is standard for commercial vehicles in this class, and both share the same 21W rating on their primary filament.
The front and rear turn signal positions on the Kenworth K100E do not share a single universal bulb type across all years, as the rear position alternates between the 1156 and 1157 depending on the model year.