Peterbilt 349 Back Up Light Bulb Size

The Peterbilt 349 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 1987.

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	1156
1987	1156 (With 4 Rectangular Headlamps)
1986	1156
1986	1156 (With Halogen Capsule Headlamps)

Bulb Specifications

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

Other Locations

Additional Notes

The 1156 is the sole bulb type listed across all back up light entries for the Peterbilt 349, covering the 1986-1987 model years.
The 1156 operates on 12 volts and draws 21 watts, placing it in the standard range for single-circuit automotive signaling and reversing applications.
As a single-filament bulb, the 1156 is dedicated to one function per socket, which aligns with its use in back up lights where only a single on/off circuit is required.
The 1156 uses a BA15s bayonet base, a single-contact fitting where the "s" denotes a single pin, distinguishing it from the dual-contact BA15d base used in some other bulb types.
The 1156 carries ANSI standardization recognized in both the United States and Canada, meaning the specification conforms to a defined interchangeability standard across those markets.
For the 1987 Peterbilt 349, the 1156 is listed under two separate fitment conditions: a general entry and one specific to vehicles equipped with four rectangular headlamps, indicating that headlamp configuration is a relevant factor in confirming the correct application.
For the 1986 Peterbilt 349, the 1156 similarly appears under two entries, with one specifying vehicles equipped with halogen capsule headlamps, again tying back up light fitment to the headlamp type installed on the vehicle.
The presence of condition-based entries across both years means that verifying the headlamp configuration of a specific vehicle is a necessary step before confirming bulb fitment, even though the bulb size itself does not change between conditions.