Peterbilt 379 Back Up Light Bulb Size

Additional Notes

• The Peterbilt 379 uses the 1156 bulb for its back up light across all model years listed in the specifications, spanning 1986 through 2007.
• The 1156 is an ANSI-standard single-filament bulb rated at 12 volts and 21 watts, recognized for use in both the United States and Canada.
• The 1156 bulb uses a BA15s bayonet base, which is a single-contact bayonet mount. This base type is not interchangeable with dual-contact bayonet variants such as the BA15d or the 1157.
• Because the 1156 is a single-filament bulb, it serves only one lighting function per socket. This distinguishes it from dual-filament bulbs, which can serve two functions, such as stop and tail, within a single housing.
• For the 1996 Peterbilt 379, the specifications record two separate entries for the back up light bulb. One entry applies to trucks equipped with four round headlamps, and the other carries no headlamp qualifier, yet both entries specify the 1156.
• The 1995 model year similarly carries two entries, one for trucks with four rectangular headlamps and one without a headlamp qualifier, with the 1156 specified in both cases.
• The 1994 model year includes a qualifier for trucks with four round headlamps alongside a general entry, both calling for the 1156 bulb.
• The 1992 and 1989 model years each contain a qualifier for trucks with halogen capsule headlamps alongside a general entry, with the 1156 specified across all such entries.
• The presence of headlamp-type qualifiers in certain model years indicates that the Peterbilt 379 was available with different headlamp configurations during those periods, though the back up light bulb specification remained the 1156 regardless of that configuration.
• The BA15s bayonet base of the 1156 requires alignment of a single pin during installation, as opposed to the offset dual-pin arrangement found on incompatible base types.