Kenworth T600A Back Up Light Bulb Size

The Kenworth T600A back up light utilizes P21W and 1156 bulb sizes for various applications across the vehicle. Available information covers the specific time range from 1986 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
1986-1997	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 T600A uses the 1156 bulb for its back up light across all listed model years from 1986 to 1997.
The 1156 is a single-filament bulb, meaning it serves one lighting function rather than combining two, such as stop and tail, into a single unit.
It operates on a 12-volt electrical system and draws 21 watts, which is consistent with standard incandescent automotive lighting output.
The 1156 uses a BA15s bayonet base, where "BA15s" denotes a single-contact bayonet fitting with a 15mm base width.
The 1156 is an ANSI-standardized bulb, recognized across the United States and Canada, which reflects broad availability in the North American market.
The BA15s base is a single-contact design, and substituting a dual-contact bayonet bulb, such as those using a BA15d base, would result in an incompatible fit.
Because the 1156 is single-filament, it is not interchangeable with the 1157, which shares a similar bayonet-style base but carries a dual-filament design and a different pin configuration.