Ford Custom Map Light Bulb Size

The Ford Custom map light uses 631, 1003, and 67 bulb sizes for the interior lighting components. Available information covers the specific time range from 1957 through 1970.

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
1967-1970	631
1964-1966	1003
1957	67

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 21W.	631
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1003
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Lower wattage variant of 1156. 12V, 8W.	67

Other Locations

Additional Notes

The Ford Custom map light bulb specifications cover model years 1957 and 1964-1970.
Three bulb types appear across these model years: the 631, the 1003, and the 67, all of which conform to ANSI standards recognized in both the United States and Canada.
All three bulb types share the BA15s bayonet base, a single-contact base design that uses a single pin offset to one side to ensure correct orientation during installation.
All three bulb types also share a 12-volt operating voltage, consistent with the 12V electrical systems standard in automotive applications of this era.
The 631 bulb is specified for the Ford Custom across model years 1967-1970. It is a single-filament bulb rated at 21W and is described as a variant of the 1156.
The 1003 bulb is specified for model years 1964-1966. It is also a single-filament, 21W bulb with a BA15s bayonet base, sharing the same wattage as the 631.
Although the 631 and 1003 share identical voltage, wattage, base type, and filament count, they carry distinct ANSI designations and are not listed interchangeably within these specifications.
The 67 bulb is specified for the 1957 model year. Rated at 8W, it draws significantly less power than the 631 and 1003, as it is a lower-wattage variant of the 1156.
Despite sharing the same BA15s bayonet base as the 631 and 1003, the 67 bulb operates at a different wattage, which affects light output and circuit load compatibility.
The physical similarity of the BA15s base across all three bulb types means cross-installation is mechanically possible, though the wattage difference of the 67 relative to the other two types makes substitution a relevant fitment consideration.