Kenworth C550 Back Up Light Bulb Size

The Kenworth C550 back up light utilizes 1156 and P21W bulb sizes for the rear illumination system. Data for the specified components covers the period from 1986 through 1994.

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
1986-1994	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 C550 uses the 1156 bulb for its back up light across the 1986-1994 model years.
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.
The 1156 uses a BA15s bayonet base, a single-contact mount where the bulb locks into the socket with a twist.
The 1156 conforms to ANSI standards recognized in both the United States and Canada.
Because the 1156 is single-filament, it is not interchangeable with the 1157, which shares the same BA15d bayonet-style housing but carries a dual-filament design and a two-contact base.