Peterbilt 377 Back Up Light Bulb Size

Additional Notes

• The Peterbilt 377 uses the 1156 bulb size across all listed model years for the back up light position, spanning 1987-2001.
• The 1156 is an ANSI-standard bulb recognized in both the United States and Canada, making it a widely available replacement type in North American markets.
• The 1156 is a single-filament bulb, meaning it serves one lighting function only, which is consistent with its application in a dedicated back up light circuit.
• The 1156 uses a BA15s bayonet base, a single-contact bayonet mount that differs from the dual-contact BA15d base used on some other automotive bulb types. Substituting a dual-contact base bulb in a BA15s socket is not compatible.
• The 1156 operates at 12 volts and 21 watts, placing it in the standard automotive low-voltage range typical of 12V vehicle electrical systems.
• For the 1994 Peterbilt 377, the 1156 bulb is specified for both the standard configuration and the variant equipped with 4 rectangular headlamps, indicating the back up light fitment is consistent regardless of headlamp type that year.
• The 1993 and 1991 model years each carry two separate entries: one for the standard configuration and one for the variant with halogen capsule headlamps. Both configurations use the 1156, confirming no change in back up light fitment between those headlamp variants.
• The 1990 model year similarly lists both a standard entry and a halogen capsule headlamp variant, with the 1156 specified for both.
• The 1989 and 1987 model years each include a variant noted as having 4 rectangular headlamps alongside a standard entry, and both variants retain the 1156 for the back up light.
• The 1988 model year includes a variant specified as having 4 round headlamps, which also uses the 1156, consistent with all other configurations across the listed years.