Kenworth W900 headlight bulbs utilize H4651, H5001 sizes for high beam and H4656, H4652, H5006 sizes for low beam applications. The replacement chart covers 1981 through 1997 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 W900 uses sealed beam headlight units across all specified model years from 1981 to 1997. Sealed beam units integrate the filament, reflector, and lens into a single assembly, meaning the entire unit is replaced rather than an individual bulb.
All sealed beam types specified for the W900 operate at 12 volts and conform to ANSI standards recognized in both the United States and Canada.
The H4651 is a 4x6-inch rectangular sealed beam unit used for the high beam position on the W900 from 1984 to 1997. It is the most consistently specified bulb type across the listed model years.
The H5001, a 4-inch square sealed beam unit, served as the high beam for the W900 in 1981-1983. The square format of the H5001 makes it physically distinct from the rectangular H4651 and H4656 units, and the two types are not interchangeable.
The low beam position on the W900 used three different sealed beam types depending on the model year: the H4652 and H4656 for 1984-1997, and the H5006 for 1981-1983. The H5006 is a 5.75-inch round sealed beam unit, which differs in both shape and size from the rectangular units used in later years.
The H4652 is a variant of the H4651, sharing the same 4x6-inch rectangular sealed beam format. Despite their physical similarity, the H4652 is designated for the low beam position while the H4651 is designated for high beam, and substituting one for the other is not supported by the specifications.
The H4656 is also a 4x6-inch rectangular sealed beam unit used in the low beam position. It appears in place of the H4652 for certain model years, including 1984, and 1989-1992, as well as 1997, indicating that the low beam specification for the W900 was not uniform across its production run.
Because the high beam and low beam positions on the W900 use distinct sealed beam designations, even units sharing the same physical format, such as the H4651 and H4652, are specified separately by position and should not be treated as interchangeable fitments.