Peterbilt 227 Back Up Light Bulb Size

Additional Notes

• The 1156 is the sole back up light bulb size listed across all model years of the Peterbilt 227 covered in these specifications.
• The 1156 is an ANSI-standard single-filament bulb rated at 12 volts and 21 watts, fitted with a BA15s bayonet base.
• The BA15s bayonet base uses a single-contact design, which is not interchangeable with dual-contact bayonet bases such as the BA15d found on two-filament bulbs.
• The Peterbilt 227 model years 1990-1994 all share the 1156 bulb for the back up light position.
• The 1994 Peterbilt 227 with 4 Rectangular Headlamps carries a separate fitment entry for the 1156, indicating that headlamp configuration is treated as a distinct fitment condition for that year.
• The 1992 Peterbilt 227 with Halogen Capsule Headlamps and the 1991 with the same headlamp configuration each carry dedicated entries, reflecting that headlamp type is a recognized fitment variable across multiple years.
• The 1990 Peterbilt 227 with 4 Round Headlamps also carries its own separate entry, consistent with the pattern of headlamp configuration being used as a fitment qualifier throughout the specifications.
• At 21 watts on a 12-volt circuit, the 1156 draws approximately 1.75 amperes, which is a standard load level for incandescent back up light applications in commercial vehicles of this era.