International S1723 Back Up Light Bulb Size

The International S1723 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 1980 to 1985.

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
1980-1985	1156

Bulb Specifications

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

Other Locations

Additional Notes

The International S1723 uses the 1156 bulb for the back up light across all listed model years, spanning 1980-1985.
The 1156 is a single-filament bulb, meaning it serves one lighting function only, which is consistent with its application in a back up light circuit.
The 1156 operates at 12 volts and 21 watts, placing it within the standard range for incandescent automotive signal and utility lighting.
The 1156 uses a BA15s bayonet base, where "BA15s" denotes a bayonet fitting with a 15mm collar and a single locating pin.
The single-pin BA15s base of the 1156 is not interchangeable with the BA15d base found on dual-filament bulbs such as the 1157, despite the two types sharing a similar physical profile.
The 1156 carries ANSI standardization recognized in both the United States and Canada, indicating the bulb conforms to a defined set of electrical and physical tolerances across those markets.