Peterbilt 359 Back Up Light Bulb Size

The Peterbilt 359 back up light uses 1156 and P21W bulb sizes for the rear illumination components. Available information covers the specific time period from 1986 through 1988.

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
1988	1156
1987	1156
1987	1156 (With 4 Round Headlamps)
1986	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 Peterbilt 359 uses the 1156 bulb for its back up light across the 1986-1988 model years.
The 1156 is an ANSI-standardized bulb type, recognized across the United States and Canada under a shared designation system.
The 1156 operates on a 12-volt electrical system and draws 21 watts, which is typical for single-filament automotive signal and reverse light applications.
As a single-filament bulb, the 1156 serves only one lighting function, distinguishing it from dual-filament types that handle two functions such as braking and running light simultaneously.
The 1156 uses a BA15s bayonet base, where "BA15s" denotes a single-contact bayonet fitting with a 15mm base width, requiring a socket designed specifically for that base type.
The 1987 Peterbilt 359 with 4 round headlamps is listed as a distinct fitment configuration, indicating that headlamp arrangement was a recognized variant affecting parts classification for that year.
The BA15s base is not interchangeable with BA15d sockets, which feature two contact pins rather than one, making base type a critical factor in bulb compatibility.