The Kenworth W900 front turn signal requires a 1157 bulb size, while rear turn signal applications use either 1156 or 1157 bulb sizes. The replacement chart covers vehicle production spanning 1981 through 1997 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 W900 front turn signal uses the 1157 bulb across all listed model years from 1981-1997, reflecting a consistent fitment specification for that position throughout the entire documented range.
The 1157 is a dual-filament bulb operating at 12 volts 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 a common choice for front turn signal positions that may also function as parking lights.
The rear turn signal position on the Kenworth W900 does not follow a uniform bulb specification across the listed years, with some model years calling for the 1157 and others calling for the 1156.
The 1156 is a single-filament bulb operating at 12 volts with a 21W output rating and a BA15s bayonet base, also conforming to ANSI standards recognized in both the United States and Canada.
Although the 1156 and 1157 share a similar physical profile and both use a bayonet-style base, their base types differ: the 1156 uses a BA15s single-contact base while the 1157 uses a BAY15d dual-contact base, making them non-interchangeable.
The offset pins on the BAY15d base of the 1157 are positioned to prevent incorrect installation in a socket designed for that bulb, which physically distinguishes it from the symmetrical BA15s base of the 1156.
For the W900 rear turn signal, the 1156 is specified for 1984, 1987, 1989-1990, and 1992, and 1994-1997, while the 1157 applies to the remaining years within the listed range.
Substituting a 1156 in place of a 1157, or vice versa, in the rear turn signal position would be incorrect for years where the socket and wiring are configured for a specific filament count and base type.
Both the 1156 and 1157 are among the most widely used bulb types in North American automotive and commercial vehicle applications, with broad availability across the ANSI-standardized market.