Kenworth T800 Back Up Light Bulb Size

The Kenworth T800 back up light utilizes P21W and 1156 bulb sizes for the rear illumination system. Data for the specified lighting components covers the range from 1987 through 1997.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1987-1997	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The Kenworth T800 backup light uses the 1156 bulb across all listed model years, spanning 1987-1997.
The 1156 is a single-filament bulb, meaning it serves one lighting function only, which is consistent with its dedicated use as a backup light.
It operates on a 12-volt electrical system at 21 watts, both standard values for automotive incandescent lighting in this application.
The 1156 uses a BA15s bayonet base, where "BA" denotes a bayonet cap fitting, "15" refers to the 15mm base width, and the lowercase "s" indicates a single contact at the base.
The BA15s single-contact base is not interchangeable with the BA15d base, which carries two contacts and is used on dual-filament bulbs such as the 1157.
The 1156 is an ANSI-standardized bulb recognized in both the United States and Canada, meaning it conforms to a defined set of electrical and physical specifications rather than being a proprietary part number.