Peterbilt 520 Back Up Light Bulb Size

The Peterbilt 520 back up light requires a 1156 bulb size for proper installation and function within the specified lighting assembly. Data for the bulb specifications covers the range from 2017 to 2019.

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
2017-2019	1156

Bulb Specifications

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

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Additional Notes

The 1156 is the specified back up light bulb for the Peterbilt 520 across the 2017-2019 model years.
The 1156 is an ANSI-standardized bulb type, meaning its physical and electrical characteristics conform to a defined North American specification recognized in both the United States and Canada.
The 1156 operates on a 12-volt electrical system and draws 21 watts, which is consistent with standard automotive incandescent backup lighting.
The bulb uses a BA15s bayonet base, a single-contact fitting where the "s" denotes a single pin, as opposed to the dual-pin BA15d variant. These two base types are not interchangeable despite their similar appearance.
The 1156 is a single-filament bulb, meaning it serves one lighting function only. This distinguishes it from dual-filament types such as the 1157, which share the same bayonet base family but carry an additional contact pin and are not a drop-in substitute.