Kenworth K100E Back Up Light Bulb Size

The Kenworth K100E back up light uses 1156 and P21W bulb sizes according to the provided data. Information for the back up light covers the range from 1985 to 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
1985-1997	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 K100E uses the 1156 bulb for its back up light across all listed model years from 1985 to 1997.
The 1156 is an ANSI-standardized bulb type recognized across the United States and Canada.
It is a single-filament bulb, meaning it serves one lighting function rather than switching between two brightness levels.
The 1156 operates on a 12-volt electrical system and draws 21 watts.
Its base type is the BA15s bayonet mount, a single-contact design where the bulb locks into the socket with a twist.
The BA15s base is not interchangeable with the BA15d bayonet base, which carries two contacts and is used on dual-filament bulbs such as the 1157.