Ford Custom Back Up Light Bulb Size

Additional Notes

• The Ford Custom backup light bulb specifications cover model years 1957 and 1964-1972.
• The 1156 bulb is the dominant type across this vehicle, appearing in every listed year from 1964-1972.
• The 1156 is an ANSI-standard single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base.
• The 1141 bulb is specified for the 1957 Ford Custom and shares the same ANSI-standard single-filament design, 12V/21W rating, and BA15s bayonet base as the 1156.
• Because the 1156 and 1141 share the same BA15s bayonet base and electrical ratings, they are physically and electrically similar, though they carry distinct ANSI part numbers and are not considered interchangeable replacements without confirming the correct designation for each model year.
• The BA15s bayonet base uses a single contact pin, which distinguishes it from the dual-pin BA15d base found on double-contact bulbs; using a double-contact bulb in a single-contact socket is not compatible.
• A single-filament design means these bulbs serve one dedicated function, in this case reverse lighting, rather than combining multiple functions such as brake and tail lighting into one bulb.
• The 21W power rating at 12V places these bulbs in a standard output range for backup lighting of that era, producing sufficient illumination for reversing without the higher wattage associated with driving or fog lamps.